valgrind.bin(1)



VALGRIND(1)                     Release 3.13.0                     VALGRIND(1)

NAME
       valgrind - a suite of tools for debugging and profiling programs

SYNOPSIS
       valgrind [valgrind-options] [your-program] [your-program-options]

DESCRIPTION
       Valgrind is a flexible program for debugging and profiling Linux
       executables. It consists of a core, which provides a synthetic CPU in
       software, and a series of debugging and profiling tools. The
       architecture is modular, so that new tools can be created easily and
       without disturbing the existing structure.

       Some of the options described below work with all Valgrind tools, and
       some only work with a few or one. The section MEMCHECK OPTIONS and
       those below it describe tool-specific options.

       This manual page covers only basic usage and options. For more
       comprehensive information, please see the HTML documentation on your
       system: $INSTALL/share/doc/valgrind/html/index.html, or online:
       http://www.valgrind.org/docs/manual/index.html.

TOOL SELECTION OPTIONS
       The single most important option.

       --tool=<toolname> [default: memcheck]
           Run the Valgrind tool called toolname, e.g. memcheck, cachegrind,
           callgrind, helgrind, drd, massif, lackey, none, exp-sgcheck,
           exp-bbv, exp-dhat, etc.

BASIC OPTIONS
       These options work with all tools.

       -h --help
           Show help for all options, both for the core and for the selected
           tool. If the option is repeated it is equivalent to giving
           --help-debug.

       --help-debug
           Same as --help, but also lists debugging options which usually are
           only of use to Valgrind's developers.

       --version
           Show the version number of the Valgrind core. Tools can have their
           own version numbers. There is a scheme in place to ensure that
           tools only execute when the core version is one they are known to
           work with. This was done to minimise the chances of strange
           problems arising from tool-vs-core version incompatibilities.

       -q, --quiet
           Run silently, and only print error messages. Useful if you are
           running regression tests or have some other automated test
           machinery.

       -v, --verbose
           Be more verbose. Gives extra information on various aspects of your
           program, such as: the shared objects loaded, the suppressions used,
           the progress of the instrumentation and execution engines, and
           warnings about unusual behaviour. Repeating the option increases
           the verbosity level.

       --trace-children=<yes|no> [default: no]
           When enabled, Valgrind will trace into sub-processes initiated via
           the exec system call. This is necessary for multi-process programs.

           Note that Valgrind does trace into the child of a fork (it would be
           difficult not to, since fork makes an identical copy of a process),
           so this option is arguably badly named. However, most children of
           fork calls immediately call exec anyway.

       --trace-children-skip=patt1,patt2,...
           This option only has an effect when --trace-children=yes is
           specified. It allows for some children to be skipped. The option
           takes a comma separated list of patterns for the names of child
           executables that Valgrind should not trace into. Patterns may
           include the metacharacters ?  and *, which have the usual meaning.

           This can be useful for pruning uninteresting branches from a tree
           of processes being run on Valgrind. But you should be careful when
           using it. When Valgrind skips tracing into an executable, it
           doesn't just skip tracing that executable, it also skips tracing
           any of that executable's child processes. In other words, the flag
           doesn't merely cause tracing to stop at the specified executables
           -- it skips tracing of entire process subtrees rooted at any of the
           specified executables.

       --trace-children-skip-by-arg=patt1,patt2,...
           This is the same as --trace-children-skip, with one difference: the
           decision as to whether to trace into a child process is made by
           examining the arguments to the child process, rather than the name
           of its executable.

       --child-silent-after-fork=<yes|no> [default: no]
           When enabled, Valgrind will not show any debugging or logging
           output for the child process resulting from a fork call. This can
           make the output less confusing (although more misleading) when
           dealing with processes that create children. It is particularly
           useful in conjunction with --trace-children=. Use of this option is
           also strongly recommended if you are requesting XML output
           (--xml=yes), since otherwise the XML from child and parent may
           become mixed up, which usually makes it useless.

       --vgdb=<no|yes|full> [default: yes]
           Valgrind will provide "gdbserver" functionality when --vgdb=yes or
           --vgdb=full is specified. This allows an external GNU GDB debugger
           to control and debug your program when it runs on Valgrind.
           --vgdb=full incurs significant performance overheads, but provides
           more precise breakpoints and watchpoints. See Debugging your
           program using Valgrind's gdbserver and GDB for a detailed
           description.

           If the embedded gdbserver is enabled but no gdb is currently being
           used, the vgdb command line utility can send "monitor commands" to
           Valgrind from a shell. The Valgrind core provides a set of Valgrind
           monitor commands. A tool can optionally provide tool specific
           monitor commands, which are documented in the tool specific
           chapter.

       --vgdb-error=<number> [default: 999999999]
           Use this option when the Valgrind gdbserver is enabled with
           --vgdb=yes or --vgdb=full. Tools that report errors will wait for
           "number" errors to be reported before freezing the program and
           waiting for you to connect with GDB. It follows that a value of
           zero will cause the gdbserver to be started before your program is
           executed. This is typically used to insert GDB breakpoints before
           execution, and also works with tools that do not report errors,
           such as Massif.

       --vgdb-stop-at=<set> [default: none]
           Use this option when the Valgrind gdbserver is enabled with
           --vgdb=yes or --vgdb=full. The Valgrind gdbserver will be invoked
           for each error after --vgdb-error have been reported. You can
           additionally ask the Valgrind gdbserver to be invoked for other
           events, specified in one of the following ways:

           o   a comma separated list of one or more of startup exit
               valgrindabexit.

               The values startup exit valgrindabexit respectively indicate to
               invoke gdbserver before your program is executed, after the
               last instruction of your program, on Valgrind abnormal exit
               (e.g. internal error, out of memory, ...).

               Note: startup and --vgdb-error=0 will both cause Valgrind
               gdbserver to be invoked before your program is executed. The
               --vgdb-error=0 will in addition cause your program to stop on
               all subsequent errors.

           o   all to specify the complete set. It is equivalent to
               --vgdb-stop-at=startup,exit,valgrindabexit.

           o   none for the empty set.

       --track-fds=<yes|no> [default: no]
           When enabled, Valgrind will print out a list of open file
           descriptors on exit or on request, via the gdbserver monitor
           command v.info open_fds. Along with each file descriptor is printed
           a stack backtrace of where the file was opened and any details
           relating to the file descriptor such as the file name or socket
           details.

       --time-stamp=<yes|no> [default: no]
           When enabled, each message is preceded with an indication of the
           elapsed wallclock time since startup, expressed as days, hours,
           minutes, seconds and milliseconds.

       --log-fd=<number> [default: 2, stderr]
           Specifies that Valgrind should send all of its messages to the
           specified file descriptor. The default, 2, is the standard error
           channel (stderr). Note that this may interfere with the client's
           own use of stderr, as Valgrind's output will be interleaved with
           any output that the client sends to stderr.

       --log-file=<filename>
           Specifies that Valgrind should send all of its messages to the
           specified file. If the file name is empty, it causes an abort.
           There are three special format specifiers that can be used in the
           file name.

           %p is replaced with the current process ID. This is very useful for
           program that invoke multiple processes. WARNING: If you use
           --trace-children=yes and your program invokes multiple processes OR
           your program forks without calling exec afterwards, and you don't
           use this specifier (or the %q specifier below), the Valgrind output
           from all those processes will go into one file, possibly jumbled
           up, and possibly incomplete. Note: If the program forks and calls
           exec afterwards, Valgrind output of the child from the period
           between fork and exec will be lost. Fortunately this gap is really
           tiny for most programs; and modern programs use posix_spawn anyway.

           %n is replaced with a file sequence number unique for this process.
           This is useful for processes that produces several files from the
           same filename template.

           %q{FOO} is replaced with the contents of the environment variable
           FOO. If the {FOO} part is malformed, it causes an abort. This
           specifier is rarely needed, but very useful in certain
           circumstances (eg. when running MPI programs). The idea is that you
           specify a variable which will be set differently for each process
           in the job, for example BPROC_RANK or whatever is applicable in
           your MPI setup. If the named environment variable is not set, it
           causes an abort. Note that in some shells, the { and } characters
           may need to be escaped with a backslash.

           %% is replaced with %.

           If an % is followed by any other character, it causes an abort.

           If the file name specifies a relative file name, it is put in the
           program's initial working directory: this is the current directory
           when the program started its execution after the fork or after the
           exec. If it specifies an absolute file name (ie. starts with '/')
           then it is put there.

       --log-socket=<ip-address:port-number>
           Specifies that Valgrind should send all of its messages to the
           specified port at the specified IP address. The port may be
           omitted, in which case port 1500 is used. If a connection cannot be
           made to the specified socket, Valgrind falls back to writing output
           to the standard error (stderr). This option is intended to be used
           in conjunction with the valgrind-listener program. For further
           details, see the commentary in the manual.

ERROR-RELATED OPTIONS
       These options are used by all tools that can report errors, e.g.
       Memcheck, but not Cachegrind.

       --xml=<yes|no> [default: no]
           When enabled, the important parts of the output (e.g. tool error
           messages) will be in XML format rather than plain text.
           Furthermore, the XML output will be sent to a different output
           channel than the plain text output. Therefore, you also must use
           one of --xml-fd, --xml-file or --xml-socket to specify where the
           XML is to be sent.

           Less important messages will still be printed in plain text, but
           because the XML output and plain text output are sent to different
           output channels (the destination of the plain text output is still
           controlled by --log-fd, --log-file and --log-socket) this should
           not cause problems.

           This option is aimed at making life easier for tools that consume
           Valgrind's output as input, such as GUI front ends. Currently this
           option works with Memcheck, Helgrind, DRD and SGcheck. The output
           format is specified in the file
           docs/internals/xml-output-protocol4.txt in the source tree for
           Valgrind 3.5.0 or later.

           The recommended options for a GUI to pass, when requesting XML
           output, are: --xml=yes to enable XML output, --xml-file to send the
           XML output to a (presumably GUI-selected) file, --log-file to send
           the plain text output to a second GUI-selected file,
           --child-silent-after-fork=yes, and -q to restrict the plain text
           output to critical error messages created by Valgrind itself. For
           example, failure to read a specified suppressions file counts as a
           critical error message. In this way, for a successful run the text
           output file will be empty. But if it isn't empty, then it will
           contain important information which the GUI user should be made
           aware of.

       --xml-fd=<number> [default: -1, disabled]
           Specifies that Valgrind should send its XML output to the specified
           file descriptor. It must be used in conjunction with --xml=yes.

       --xml-file=<filename>
           Specifies that Valgrind should send its XML output to the specified
           file. It must be used in conjunction with --xml=yes. Any %p or %q
           sequences appearing in the filename are expanded in exactly the
           same way as they are for --log-file. See the description of --log-
           file for details.

       --xml-socket=<ip-address:port-number>
           Specifies that Valgrind should send its XML output the specified
           port at the specified IP address. It must be used in conjunction
           with --xml=yes. The form of the argument is the same as that used
           by --log-socket. See the description of --log-socket for further
           details.

       --xml-user-comment=<string>
           Embeds an extra user comment string at the start of the XML output.
           Only works when --xml=yes is specified; ignored otherwise.

       --demangle=<yes|no> [default: yes]
           Enable/disable automatic demangling (decoding) of C++ names.
           Enabled by default. When enabled, Valgrind will attempt to
           translate encoded C++ names back to something approaching the
           original. The demangler handles symbols mangled by g++ versions
           2.X, 3.X and 4.X.

           An important fact about demangling is that function names mentioned
           in suppressions files should be in their mangled form. Valgrind
           does not demangle function names when searching for applicable
           suppressions, because to do otherwise would make suppression file
           contents dependent on the state of Valgrind's demangling machinery,
           and also slow down suppression matching.

       --num-callers=<number> [default: 12]
           Specifies the maximum number of entries shown in stack traces that
           identify program locations. Note that errors are commoned up using
           only the top four function locations (the place in the current
           function, and that of its three immediate callers). So this doesn't
           affect the total number of errors reported.

           The maximum value for this is 500. Note that higher settings will
           make Valgrind run a bit more slowly and take a bit more memory, but
           can be useful when working with programs with deeply-nested call
           chains.

       --unw-stack-scan-thresh=<number> [default: 0] ,
       --unw-stack-scan-frames=<number> [default: 5]
           Stack-scanning support is available only on ARM targets.

           These flags enable and control stack unwinding by stack scanning.
           When the normal stack unwinding mechanisms -- usage of Dwarf CFI
           records, and frame-pointer following -- fail, stack scanning may be
           able to recover a stack trace.

           Note that stack scanning is an imprecise, heuristic mechanism that
           may give very misleading results, or none at all. It should be used
           only in emergencies, when normal unwinding fails, and it is
           important to nevertheless have stack traces.

           Stack scanning is a simple technique: the unwinder reads words from
           the stack, and tries to guess which of them might be return
           addresses, by checking to see if they point just after ARM or Thumb
           call instructions. If so, the word is added to the backtrace.

           The main danger occurs when a function call returns, leaving its
           return address exposed, and a new function is called, but the new
           function does not overwrite the old address. The result of this is
           that the backtrace may contain entries for functions which have
           already returned, and so be very confusing.

           A second limitation of this implementation is that it will scan
           only the page (4KB, normally) containing the starting stack
           pointer. If the stack frames are large, this may result in only a
           few (or not even any) being present in the trace. Also, if you are
           unlucky and have an initial stack pointer near the end of its
           containing page, the scan may miss all interesting frames.

           By default stack scanning is disabled. The normal use case is to
           ask for it when a stack trace would otherwise be very short. So, to
           enable it, use --unw-stack-scan-thresh=number. This requests
           Valgrind to try using stack scanning to "extend" stack traces which
           contain fewer than number frames.

           If stack scanning does take place, it will only generate at most
           the number of frames specified by --unw-stack-scan-frames.
           Typically, stack scanning generates so many garbage entries that
           this value is set to a low value (5) by default. In no case will a
           stack trace larger than the value specified by --num-callers be
           created.

       --error-limit=<yes|no> [default: yes]
           When enabled, Valgrind stops reporting errors after 10,000,000 in
           total, or 1,000 different ones, have been seen. This is to stop the
           error tracking machinery from becoming a huge performance overhead
           in programs with many errors.

       --error-exitcode=<number> [default: 0]
           Specifies an alternative exit code to return if Valgrind reported
           any errors in the run. When set to the default value (zero), the
           return value from Valgrind will always be the return value of the
           process being simulated. When set to a nonzero value, that value is
           returned instead, if Valgrind detects any errors. This is useful
           for using Valgrind as part of an automated test suite, since it
           makes it easy to detect test cases for which Valgrind has reported
           errors, just by inspecting return codes.

       --error-markers=<begin>,<end> [default: none]
           When errors are output as plain text (i.e. XML not used),
           --error-markers instructs to output a line containing the begin
           (end) string before (after) each error.

           Such marker lines facilitate searching for errors and/or extracting
           errors in an output file that contain valgrind errors mixed with
           the program output.

           Note that empty markers are accepted. So, only using a begin (or an
           end) marker is possible.

       --sigill-diagnostics=<yes|no> [default: yes]
           Enable/disable printing of illegal instruction diagnostics. Enabled
           by default, but defaults to disabled when --quiet is given. The
           default can always be explicitly overridden by giving this option.

           When enabled, a warning message will be printed, along with some
           diagnostics, whenever an instruction is encountered that Valgrind
           cannot decode or translate, before the program is given a SIGILL
           signal. Often an illegal instruction indicates a bug in the program
           or missing support for the particular instruction in Valgrind. But
           some programs do deliberately try to execute an instruction that
           might be missing and trap the SIGILL signal to detect processor
           features. Using this flag makes it possible to avoid the diagnostic
           output that you would otherwise get in such cases.

       --show-below-main=<yes|no> [default: no]
           By default, stack traces for errors do not show any functions that
           appear beneath main because most of the time it's uninteresting C
           library stuff and/or gobbledygook. Alternatively, if main is not
           present in the stack trace, stack traces will not show any
           functions below main-like functions such as glibc's
           __libc_start_main. Furthermore, if main-like functions are present
           in the trace, they are normalised as (below main), in order to make
           the output more deterministic.

           If this option is enabled, all stack trace entries will be shown
           and main-like functions will not be normalised.

       --fullpath-after=<string> [default: don't show source paths]
           By default Valgrind only shows the filenames in stack traces, but
           not full paths to source files. When using Valgrind in large
           projects where the sources reside in multiple different
           directories, this can be inconvenient.  --fullpath-after provides a
           flexible solution to this problem. When this option is present, the
           path to each source file is shown, with the following all-important
           caveat: if string is found in the path, then the path up to and
           including string is omitted, else the path is shown unmodified.
           Note that string is not required to be a prefix of the path.

           For example, consider a file named
           /home/janedoe/blah/src/foo/bar/xyzzy.c. Specifying
           --fullpath-after=/home/janedoe/blah/src/ will cause Valgrind to
           show the name as foo/bar/xyzzy.c.

           Because the string is not required to be a prefix,
           --fullpath-after=src/ will produce the same output. This is useful
           when the path contains arbitrary machine-generated characters. For
           example, the path /my/build/dir/C32A1B47/blah/src/foo/xyzzy can be
           pruned to foo/xyzzy using --fullpath-after=/blah/src/.

           If you simply want to see the full path, just specify an empty
           string: --fullpath-after=. This isn't a special case, merely a
           logical consequence of the above rules.

           Finally, you can use --fullpath-after multiple times. Any
           appearance of it causes Valgrind to switch to producing full paths
           and applying the above filtering rule. Each produced path is
           compared against all the --fullpath-after-specified strings, in the
           order specified. The first string to match causes the path to be
           truncated as described above. If none match, the full path is
           shown. This facilitates chopping off prefixes when the sources are
           drawn from a number of unrelated directories.

       --extra-debuginfo-path=<path> [default: undefined and unused]
           By default Valgrind searches in several well-known paths for debug
           objects, such as /usr/lib/debug/.

           However, there may be scenarios where you may wish to put debug
           objects at an arbitrary location, such as external storage when
           running Valgrind on a mobile device with limited local storage.
           Another example might be a situation where you do not have
           permission to install debug object packages on the system where you
           are running Valgrind.

           In these scenarios, you may provide an absolute path as an extra,
           final place for Valgrind to search for debug objects by specifying
           --extra-debuginfo-path=/path/to/debug/objects. The given path will
           be prepended to the absolute path name of the searched-for object.
           For example, if Valgrind is looking for the debuginfo for
           /w/x/y/zz.so and --extra-debuginfo-path=/a/b/c is specified, it
           will look for a debug object at /a/b/c/w/x/y/zz.so.

           This flag should only be specified once. If it is specified
           multiple times, only the last instance is honoured.

       --debuginfo-server=ipaddr:port [default: undefined and unused]
           This is a new, experimental, feature introduced in version 3.9.0.

           In some scenarios it may be convenient to read debuginfo from
           objects stored on a different machine. With this flag, Valgrind
           will query a debuginfo server running on ipaddr and listening on
           port port, if it cannot find the debuginfo object in the local
           filesystem.

           The debuginfo server must accept TCP connections on port port. The
           debuginfo server is contained in the source file
           auxprogs/valgrind-di-server.c. It will only serve from the
           directory it is started in.  port defaults to 1500 in both client
           and server if not specified.

           If Valgrind looks for the debuginfo for /w/x/y/zz.so by using the
           debuginfo server, it will strip the pathname components and merely
           request zz.so on the server. That in turn will look only in its
           current working directory for a matching debuginfo object.

           The debuginfo data is transmitted in small fragments (8 KB) as
           requested by Valgrind. Each block is compressed using LZO to reduce
           transmission time. The implementation has been tuned for best
           performance over a single-stage 802.11g (WiFi) network link.

           Note that checks for matching primary vs debug objects, using GNU
           debuglink CRC scheme, are performed even when using the debuginfo
           server. To disable such checking, you need to also specify
           --allow-mismatched-debuginfo=yes.

           By default the Valgrind build system will build valgrind-di-server
           for the target platform, which is almost certainly not what you
           want. So far we have been unable to find out how to get
           automake/autoconf to build it for the build platform. If you want
           to use it, you will have to recompile it by hand using the command
           shown at the top of auxprogs/valgrind-di-server.c.

       --allow-mismatched-debuginfo=no|yes [no]
           When reading debuginfo from separate debuginfo objects, Valgrind
           will by default check that the main and debuginfo objects match,
           using the GNU debuglink mechanism. This guarantees that it does not
           read debuginfo from out of date debuginfo objects, and also ensures
           that Valgrind can't crash as a result of mismatches.

           This check can be overridden using
           --allow-mismatched-debuginfo=yes. This may be useful when the
           debuginfo and main objects have not been split in the proper way.
           Be careful when using this, though: it disables all consistency
           checking, and Valgrind has been observed to crash when the main and
           debuginfo objects don't match.

       --suppressions=<filename> [default: $PREFIX/lib/valgrind/default.supp]
           Specifies an extra file from which to read descriptions of errors
           to suppress. You may use up to 100 extra suppression files.

       --gen-suppressions=<yes|no|all> [default: no]
           When set to yes, Valgrind will pause after every error shown and
           print the line:

                   ---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----

           Pressing Ret, or N Ret or n Ret, causes Valgrind continue execution
           without printing a suppression for this error.

           Pressing Y Ret or y Ret causes Valgrind to write a suppression for
           this error. You can then cut and paste it into a suppression file
           if you don't want to hear about the error in the future.

           When set to all, Valgrind will print a suppression for every
           reported error, without querying the user.

           This option is particularly useful with C++ programs, as it prints
           out the suppressions with mangled names, as required.

           Note that the suppressions printed are as specific as possible. You
           may want to common up similar ones, by adding wildcards to function
           names, and by using frame-level wildcards. The wildcarding
           facilities are powerful yet flexible, and with a bit of careful
           editing, you may be able to suppress a whole family of related
           errors with only a few suppressions.

           Sometimes two different errors are suppressed by the same
           suppression, in which case Valgrind will output the suppression
           more than once, but you only need to have one copy in your
           suppression file (but having more than one won't cause problems).
           Also, the suppression name is given as <insert a suppression name
           here>; the name doesn't really matter, it's only used with the -v
           option which prints out all used suppression records.

       --input-fd=<number> [default: 0, stdin]
           When using --gen-suppressions=yes, Valgrind will stop so as to read
           keyboard input from you when each error occurs. By default it reads
           from the standard input (stdin), which is problematic for programs
           which close stdin. This option allows you to specify an alternative
           file descriptor from which to read input.

       --dsymutil=no|yes [yes]
           This option is only relevant when running Valgrind on Mac OS X.

           Mac OS X uses a deferred debug information (debuginfo) linking
           scheme. When object files containing debuginfo are linked into a
           .dylib or an executable, the debuginfo is not copied into the final
           file. Instead, the debuginfo must be linked manually by running
           dsymutil, a system-provided utility, on the executable or .dylib.
           The resulting combined debuginfo is placed in a directory alongside
           the executable or .dylib, but with the extension .dSYM.

           With --dsymutil=no, Valgrind will detect cases where the .dSYM
           directory is either missing, or is present but does not appear to
           match the associated executable or .dylib, most likely because it
           is out of date. In these cases, Valgrind will print a warning
           message but take no further action.

           With --dsymutil=yes, Valgrind will, in such cases, automatically
           run dsymutil as necessary to bring the debuginfo up to date. For
           all practical purposes, if you always use --dsymutil=yes, then
           there is never any need to run dsymutil manually or as part of your
           applications's build system, since Valgrind will run it as
           necessary.

           Valgrind will not attempt to run dsymutil on any executable or
           library in /usr/, /bin/, /sbin/, /opt/, /sw/, /System/, /Library/
           or /Applications/ since dsymutil will always fail in such
           situations. It fails both because the debuginfo for such
           pre-installed system components is not available anywhere, and also
           because it would require write privileges in those directories.

           Be careful when using --dsymutil=yes, since it will cause
           pre-existing .dSYM directories to be silently deleted and
           re-created. Also note that dsymutil is quite slow, sometimes
           excessively so.

       --max-stackframe=<number> [default: 2000000]
           The maximum size of a stack frame. If the stack pointer moves by
           more than this amount then Valgrind will assume that the program is
           switching to a different stack.

           You may need to use this option if your program has large
           stack-allocated arrays. Valgrind keeps track of your program's
           stack pointer. If it changes by more than the threshold amount,
           Valgrind assumes your program is switching to a different stack,
           and Memcheck behaves differently than it would for a stack pointer
           change smaller than the threshold. Usually this heuristic works
           well. However, if your program allocates large structures on the
           stack, this heuristic will be fooled, and Memcheck will
           subsequently report large numbers of invalid stack accesses. This
           option allows you to change the threshold to a different value.

           You should only consider use of this option if Valgrind's debug
           output directs you to do so. In that case it will tell you the new
           threshold you should specify.

           In general, allocating large structures on the stack is a bad idea,
           because you can easily run out of stack space, especially on
           systems with limited memory or which expect to support large
           numbers of threads each with a small stack, and also because the
           error checking performed by Memcheck is more effective for
           heap-allocated data than for stack-allocated data. If you have to
           use this option, you may wish to consider rewriting your code to
           allocate on the heap rather than on the stack.

       --main-stacksize=<number> [default: use current 'ulimit' value]
           Specifies the size of the main thread's stack.

           To simplify its memory management, Valgrind reserves all required
           space for the main thread's stack at startup. That means it needs
           to know the required stack size at startup.

           By default, Valgrind uses the current "ulimit" value for the stack
           size, or 16 MB, whichever is lower. In many cases this gives a
           stack size in the range 8 to 16 MB, which almost never overflows
           for most applications.

           If you need a larger total stack size, use --main-stacksize to
           specify it. Only set it as high as you need, since reserving far
           more space than you need (that is, hundreds of megabytes more than
           you need) constrains Valgrind's memory allocators and may reduce
           the total amount of memory that Valgrind can use. This is only
           really of significance on 32-bit machines.

           On Linux, you may request a stack of size up to 2GB. Valgrind will
           stop with a diagnostic message if the stack cannot be allocated.

           --main-stacksize only affects the stack size for the program's
           initial thread. It has no bearing on the size of thread stacks, as
           Valgrind does not allocate those.

           You may need to use both --main-stacksize and --max-stackframe
           together. It is important to understand that --main-stacksize sets
           the maximum total stack size, whilst --max-stackframe specifies the
           largest size of any one stack frame. You will have to work out the
           --main-stacksize value for yourself (usually, if your applications
           segfaults). But Valgrind will tell you the needed --max-stackframe
           size, if necessary.

           As discussed further in the description of --max-stackframe, a
           requirement for a large stack is a sign of potential portability
           problems. You are best advised to place all large data in
           heap-allocated memory.

       --max-threads=<number> [default: 500]
           By default, Valgrind can handle to up to 500 threads. Occasionally,
           that number is too small. Use this option to provide a different
           limit. E.g.  --max-threads=3000.

MALLOC()-RELATED OPTIONS
       For tools that use their own version of malloc (e.g. Memcheck, Massif,
       Helgrind, DRD), the following options apply.

       --alignment=<number> [default: 8 or 16, depending on the platform]
           By default Valgrind's malloc, realloc, etc, return a block whose
           starting address is 8-byte aligned or 16-byte aligned (the value
           depends on the platform and matches the platform default). This
           option allows you to specify a different alignment. The supplied
           value must be greater than or equal to the default, less than or
           equal to 4096, and must be a power of two.

       --redzone-size=<number> [default: depends on the tool]
           Valgrind's malloc, realloc, etc, add padding blocks before and
           after each heap block allocated by the program being run. Such
           padding blocks are called redzones. The default value for the
           redzone size depends on the tool. For example, Memcheck adds and
           protects a minimum of 16 bytes before and after each block
           allocated by the client. This allows it to detect block underruns
           or overruns of up to 16 bytes.

           Increasing the redzone size makes it possible to detect overruns of
           larger distances, but increases the amount of memory used by
           Valgrind. Decreasing the redzone size will reduce the memory needed
           by Valgrind but also reduces the chances of detecting
           over/underruns, so is not recommended.

       --xtree-memory=none|allocs|full [none]
           Tools replacing Valgrind's malloc, realloc, etc, can optionally
           produce an execution tree detailing which piece of code is
           responsible for heap memory usage. See ???  for a detailed
           explanation about execution trees.

           When set to none, no memory execution tree is produced.

           When set to allocs, the memory execution tree gives the current
           number of allocated bytes and the current number of allocated
           blocks.

           When set to full, the memory execution tree gives 6 different
           measurements : the current number of allocated bytes and blocks
           (same values as for allocs), the total number of allocated bytes
           and blocks, the total number of freed bytes and blocks.

           Note that the overhead in cpu and memory to produce an xtree
           depends on the tool. The overhead in cpu is small for the value
           allocs, as the information needed to produce this report is
           maintained in any case by the tool. For massif and helgrind,
           specifying full implies to capture a stack trace for each free
           operation, while normally these tools only capture an allocation
           stack trace. For memcheck, the cpu overhead for the value full is
           small, as this can only be used in combination with
           --keep-stacktraces=alloc-and-free or
           --keep-stacktraces=alloc-then-free, which already records a stack
           trace for each free operation. The memory overhead varies between 5
           and 10 words per unique stacktrace in the xtree, plus the memory
           needed to record the stack trace for the free operations, if needed
           specifically for the xtree.

       --xtree-memory-file=<filename> [default: xtmemory.kcg.%p]
           Specifies that Valgrind should produce the xtree memory report in
           the specified file. Any %p or %q sequences appearing in the
           filename are expanded in exactly the same way as they are for
           --log-file. See the description of --log-file for details.

           If the filename contains the extension .ms, then the produced file
           format will be a massif output file format. If the filename
           contains the extension .kcg or no extension is provided or
           recognised, then the produced file format will be a callgrind
           output format.

           See ???  for a detailed explanation about execution trees formats.

UNCOMMON OPTIONS
       These options apply to all tools, as they affect certain obscure
       workings of the Valgrind core. Most people won't need to use them.

       --smc-check=<none|stack|all|all-non-file> [default: all-non-file for
       x86/amd64/s390x, stack for other archs]
           This option controls Valgrind's detection of self-modifying code.
           If no checking is done, when a program executes some code, then
           overwrites it with new code, and executes the new code, Valgrind
           will continue to execute the translations it made for the old code.
           This will likely lead to incorrect behaviour and/or crashes.

           For "modern" architectures -- anything that's not x86, amd64 or
           s390x -- the default is stack. This is because a correct program
           must take explicit action to reestablish D-I cache coherence
           following code modification. Valgrind observes and honours such
           actions, with the result that self-modifying code is transparently
           handled with zero extra cost.

           For x86, amd64 and s390x, the program is not required to notify the
           hardware of required D-I coherence syncing. Hence the default is
           all-non-file, which covers the normal case of generating code into
           an anonymous (non-file-backed) mmap'd area.

           The meanings of the four available settings are as follows. No
           detection (none), detect self-modifying code on the stack (which is
           used by GCC to implement nested functions) (stack), detect
           self-modifying code everywhere (all), and detect self-modifying
           code everywhere except in file-backed mappings (all-non-file).

           Running with all will slow Valgrind down noticeably. Running with
           none will rarely speed things up, since very little code gets
           dynamically generated in most programs. The
           VALGRIND_DISCARD_TRANSLATIONS client request is an alternative to
           --smc-check=all and --smc-check=all-non-file that requires more
           programmer effort but allows Valgrind to run your program faster,
           by telling it precisely when translations need to be re-made.

           --smc-check=all-non-file provides a cheaper but more limited
           version of --smc-check=all. It adds checks to any translations that
           do not originate from file-backed memory mappings. Typical
           applications that generate code, for example JITs in web browsers,
           generate code into anonymous mmaped areas, whereas the "fixed" code
           of the browser always lives in file-backed mappings.
           --smc-check=all-non-file takes advantage of this observation,
           limiting the overhead of checking to code which is likely to be JIT
           generated.

       --read-inline-info=<yes|no> [default: see below]
           When enabled, Valgrind will read information about inlined function
           calls from DWARF3 debug info. This slows Valgrind startup and makes
           it use more memory (typically for each inlined piece of code, 6
           words and space for the function name), but it results in more
           descriptive stacktraces. For the 3.10.0 release, this functionality
           is enabled by default only for Linux, Android and Solaris targets
           and only for the tools Memcheck, Helgrind and DRD. Here is an
           example of some stacktraces with --read-inline-info=no:

               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x80484EA: main (inlinfo.c:6)
               ==15380==
               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x8048550: fun_noninline (inlinfo.c:6)
               ==15380==    by 0x804850E: main (inlinfo.c:34)
               ==15380==
               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x8048520: main (inlinfo.c:6)

           And here are the same errors with --read-inline-info=yes:

               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x80484EA: fun_d (inlinfo.c:6)
               ==15377==    by 0x80484EA: fun_c (inlinfo.c:14)
               ==15377==    by 0x80484EA: fun_b (inlinfo.c:20)
               ==15377==    by 0x80484EA: fun_a (inlinfo.c:26)
               ==15377==    by 0x80484EA: main (inlinfo.c:33)
               ==15377==
               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x8048550: fun_d (inlinfo.c:6)
               ==15377==    by 0x8048550: fun_noninline (inlinfo.c:41)
               ==15377==    by 0x804850E: main (inlinfo.c:34)
               ==15377==
               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x8048520: fun_d (inlinfo.c:6)
               ==15377==    by 0x8048520: main (inlinfo.c:35)

       --read-var-info=<yes|no> [default: no]
           When enabled, Valgrind will read information about variable types
           and locations from DWARF3 debug info. This slows Valgrind startup
           significantly and makes it use significantly more memory, but for
           the tools that can take advantage of it (Memcheck, Helgrind, DRD)
           it can result in more precise error messages. For example, here are
           some standard errors issued by Memcheck:

               ==15363== Uninitialised byte(s) found during client check request
               ==15363==    at 0x80484A9: croak (varinfo1.c:28)
               ==15363==    by 0x8048544: main (varinfo1.c:55)
               ==15363==  Address 0x80497f7 is 7 bytes inside data symbol "global_i2"
               ==15363==
               ==15363== Uninitialised byte(s) found during client check request
               ==15363==    at 0x80484A9: croak (varinfo1.c:28)
               ==15363==    by 0x8048550: main (varinfo1.c:56)
               ==15363==  Address 0xbea0d0cc is on thread 1's stack
               ==15363==  in frame #1, created by main (varinfo1.c:45)

           And here are the same errors with --read-var-info=yes:

               ==15370== Uninitialised byte(s) found during client check request
               ==15370==    at 0x80484A9: croak (varinfo1.c:28)
               ==15370==    by 0x8048544: main (varinfo1.c:55)
               ==15370==  Location 0x80497f7 is 0 bytes inside global_i2[7],
               ==15370==  a global variable declared at varinfo1.c:41
               ==15370==
               ==15370== Uninitialised byte(s) found during client check request
               ==15370==    at 0x80484A9: croak (varinfo1.c:28)
               ==15370==    by 0x8048550: main (varinfo1.c:56)
               ==15370==  Location 0xbeb4a0cc is 0 bytes inside local var "local"
               ==15370==  declared at varinfo1.c:46, in frame #1 of thread 1

       --vgdb-poll=<number> [default: 5000]
           As part of its main loop, the Valgrind scheduler will poll to check
           if some activity (such as an external command or some input from a
           gdb) has to be handled by gdbserver. This activity poll will be
           done after having run the given number of basic blocks (or slightly
           more than the given number of basic blocks). This poll is quite
           cheap so the default value is set relatively low. You might further
           decrease this value if vgdb cannot use ptrace system call to
           interrupt Valgrind if all threads are (most of the time) blocked in
           a system call.

       --vgdb-shadow-registers=no|yes [default: no]
           When activated, gdbserver will expose the Valgrind shadow registers
           to GDB. With this, the value of the Valgrind shadow registers can
           be examined or changed using GDB. Exposing shadow registers only
           works with GDB version 7.1 or later.

       --vgdb-prefix=<prefix> [default: /tmp/vgdb-pipe]
           To communicate with gdb/vgdb, the Valgrind gdbserver creates 3
           files (2 named FIFOs and a mmap shared memory file). The prefix
           option controls the directory and prefix for the creation of these
           files.

       --run-libc-freeres=<yes|no> [default: yes]
           This option is only relevant when running Valgrind on Linux.

           The GNU C library (libc.so), which is used by all programs, may
           allocate memory for its own uses. Usually it doesn't bother to free
           that memory when the program ends--there would be no point, since
           the Linux kernel reclaims all process resources when a process
           exits anyway, so it would just slow things down.

           The glibc authors realised that this behaviour causes leak
           checkers, such as Valgrind, to falsely report leaks in glibc, when
           a leak check is done at exit. In order to avoid this, they provided
           a routine called __libc_freeres specifically to make glibc release
           all memory it has allocated. Memcheck therefore tries to run
           __libc_freeres at exit.

           Unfortunately, in some very old versions of glibc, __libc_freeres
           is sufficiently buggy to cause segmentation faults. This was
           particularly noticeable on Red Hat 7.1. So this option is provided
           in order to inhibit the run of __libc_freeres. If your program
           seems to run fine on Valgrind, but segfaults at exit, you may find
           that --run-libc-freeres=no fixes that, although at the cost of
           possibly falsely reporting space leaks in libc.so.

       --run-cxx-freeres=<yes|no> [default: yes]
           This option is only relevant when running Valgrind on Linux or
           Solaris C++ programs.

           The GNU Standard C++ library (libstdc++.so), which is used by all
           C++ programs compiled with g++, may allocate memory for its own
           uses. Usually it doesn't bother to free that memory when the
           program ends--there would be no point, since the kernel reclaims
           all process resources when a process exits anyway, so it would just
           slow things down.

           The gcc authors realised that this behaviour causes leak checkers,
           such as Valgrind, to falsely report leaks in libstdc++, when a leak
           check is done at exit. In order to avoid this, they provided a
           routine called __gnu_cxx::__freeres specifically to make libstdc++
           release all memory it has allocated. Memcheck therefore tries to
           run __gnu_cxx::__freeres at exit.

           For the sake of flexibility and unforeseen problems with
           __gnu_cxx::__freeres, option --run-cxx-freeres=no exists, although
           at the cost of possibly falsely reporting space leaks in
           libstdc++.so.

       --sim-hints=hint1,hint2,...
           Pass miscellaneous hints to Valgrind which slightly modify the
           simulated behaviour in nonstandard or dangerous ways, possibly to
           help the simulation of strange features. By default no hints are
           enabled. Use with caution! Currently known hints are:

           o   lax-ioctls: Be very lax about ioctl handling; the only
               assumption is that the size is correct. Doesn't require the
               full buffer to be initialised when writing. Without this, using
               some device drivers with a large number of strange ioctl
               commands becomes very tiresome.

           o   fuse-compatible: Enable special handling for certain system
               calls that may block in a FUSE file-system. This may be
               necessary when running Valgrind on a multi-threaded program
               that uses one thread to manage a FUSE file-system and another
               thread to access that file-system.

           o   enable-outer: Enable some special magic needed when the program
               being run is itself Valgrind.

           o   no-inner-prefix: Disable printing a prefix > in front of each
               stdout or stderr output line in an inner Valgrind being run by
               an outer Valgrind. This is useful when running Valgrind
               regression tests in an outer/inner setup. Note that the prefix
               > will always be printed in front of the inner debug logging
               lines.

           o   no-nptl-pthread-stackcache: This hint is only relevant when
               running Valgrind on Linux.

               The GNU glibc pthread library (libpthread.so), which is used by
               pthread programs, maintains a cache of pthread stacks. When a
               pthread terminates, the memory used for the pthread stack and
               some thread local storage related data structure are not always
               directly released. This memory is kept in a cache (up to a
               certain size), and is re-used if a new thread is started.

               This cache causes the helgrind tool to report some false
               positive race condition errors on this cached memory, as
               helgrind does not understand the internal glibc cache
               synchronisation primitives. So, when using helgrind, disabling
               the cache helps to avoid false positive race conditions, in
               particular when using thread local storage variables (e.g.
               variables using the __thread qualifier).

               When using the memcheck tool, disabling the cache ensures the
               memory used by glibc to handle __thread variables is directly
               released when a thread terminates.

               Note: Valgrind disables the cache using some internal knowledge
               of the glibc stack cache implementation and by examining the
               debug information of the pthread library. This technique is
               thus somewhat fragile and might not work for all glibc
               versions. This has been successfully tested with various glibc
               versions (e.g. 2.11, 2.16, 2.18) on various platforms.

           o   lax-doors: (Solaris only) Be very lax about door syscall
               handling over unrecognised door file descriptors. Does not
               require that full buffer is initialised when writing. Without
               this, programs using libdoor(3LIB) functionality with
               completely proprietary semantics may report large number of
               false positives.

           o   fallback-llsc: (MIPS and ARM64 only): Enables an alternative
               implementation of Load-Linked (LL) and Store-Conditional (SC)
               instructions. The standard implementation gives more correct
               behaviour, but can cause indefinite looping on certain
               processor implementations that are intolerant of extra memory
               references between LL and SC. So far this is known only to
               happen on Cavium 3 cores. You should not need to use this flag,
               since the relevant cores are detected at startup and the
               alternative implementation is automatically enabled if
               necessary. There is no equivalent anti-flag: you cannot
               force-disable the alternative implementation, if it is
               automatically enabled. The underlying problem exists because
               the "standard" implementation of LL and SC is done by copying
               through LL and SC instructions into the instrumented code.
               However, tools may insert extra instrumentation memory
               references in between the LL and SC instructions. These memory
               references are not present in the original uninstrumented code,
               and their presence in the instrumented code can cause the SC
               instructions to persistently fail, leading to indefinite
               looping in LL-SC blocks. The alternative implementation gives
               correct behaviour of LL and SC instructions between threads in
               a process, up to and including the ABA scenario. It also gives
               correct behaviour between a Valgrinded thread and a
               non-Valgrinded thread running in a different process, that
               communicate via shared memory, but only up to and including
               correct CAS behaviour -- in this case the ABA scenario may not
               be correctly handled.

       --fair-sched=<no|yes|try> [default: no]
           The --fair-sched option controls the locking mechanism used by
           Valgrind to serialise thread execution. The locking mechanism
           controls the way the threads are scheduled, and different settings
           give different trade-offs between fairness and performance. For
           more details about the Valgrind thread serialisation scheme and its
           impact on performance and thread scheduling, see Scheduling and
           Multi-Thread Performance.

           o   The value --fair-sched=yes activates a fair scheduler. In
               short, if multiple threads are ready to run, the threads will
               be scheduled in a round robin fashion. This mechanism is not
               available on all platforms or Linux versions. If not available,
               using --fair-sched=yes will cause Valgrind to terminate with an
               error.

               You may find this setting improves overall responsiveness if
               you are running an interactive multithreaded program, for
               example a web browser, on Valgrind.

           o   The value --fair-sched=try activates fair scheduling if
               available on the platform. Otherwise, it will automatically
               fall back to --fair-sched=no.

           o   The value --fair-sched=no activates a scheduler which does not
               guarantee fairness between threads ready to run, but which in
               general gives the highest performance.

       --kernel-variant=variant1,variant2,...
           Handle system calls and ioctls arising from minor variants of the
           default kernel for this platform. This is useful for running on
           hacked kernels or with kernel modules which support nonstandard
           ioctls, for example. Use with caution. If you don't understand what
           this option does then you almost certainly don't need it. Currently
           known variants are:

           o   bproc: support the sys_broc system call on x86. This is for
               running on BProc, which is a minor variant of standard Linux
               which is sometimes used for building clusters.

           o   android-no-hw-tls: some versions of the Android emulator for
               ARM do not provide a hardware TLS (thread-local state)
               register, and Valgrind crashes at startup. Use this variant to
               select software support for TLS.

           o   android-gpu-sgx5xx: use this to support handling of proprietary
               ioctls for the PowerVR SGX 5XX series of GPUs on Android
               devices. Failure to select this does not cause stability
               problems, but may cause Memcheck to report false errors after
               the program performs GPU-specific ioctls.

           o   android-gpu-adreno3xx: similarly, use this to support handling
               of proprietary ioctls for the Qualcomm Adreno 3XX series of
               GPUs on Android devices.

       --merge-recursive-frames=<number> [default: 0]
           Some recursive algorithms, for example balanced binary tree
           implementations, create many different stack traces, each
           containing cycles of calls. A cycle is defined as two identical
           program counter values separated by zero or more other program
           counter values. Valgrind may then use a lot of memory to store all
           these stack traces. This is a poor use of memory considering that
           such stack traces contain repeated uninteresting recursive calls
           instead of more interesting information such as the function that
           has initiated the recursive call.

           The option --merge-recursive-frames=<number> instructs Valgrind to
           detect and merge recursive call cycles having a size of up to
           <number> frames. When such a cycle is detected, Valgrind records
           the cycle in the stack trace as a unique program counter.

           The value 0 (the default) causes no recursive call merging. A value
           of 1 will cause stack traces of simple recursive algorithms (for
           example, a factorial implementation) to be collapsed. A value of 2
           will usually be needed to collapse stack traces produced by
           recursive algorithms such as binary trees, quick sort, etc. Higher
           values might be needed for more complex recursive algorithms.

           Note: recursive calls are detected by analysis of program counter
           values. They are not detected by looking at function names.

       --num-transtab-sectors=<number> [default: 6 for Android platforms, 16
       for all others]
           Valgrind translates and instruments your program's machine code in
           small fragments (basic blocks). The translations are stored in a
           translation cache that is divided into a number of sections
           (sectors). If the cache is full, the sector containing the oldest
           translations is emptied and reused. If these old translations are
           needed again, Valgrind must re-translate and re-instrument the
           corresponding machine code, which is expensive. If the "executed
           instructions" working set of a program is big, increasing the
           number of sectors may improve performance by reducing the number of
           re-translations needed. Sectors are allocated on demand. Once
           allocated, a sector can never be freed, and occupies considerable
           space, depending on the tool and the value of
           --avg-transtab-entry-size (about 40 MB per sector for Memcheck).
           Use the option --stats=yes to obtain precise information about the
           memory used by a sector and the allocation and recycling of
           sectors.

       --avg-transtab-entry-size=<number> [default: 0, meaning use tool
       provided default]
           Average size of translated basic block. This average size is used
           to dimension the size of a sector. Each tool provides a default
           value to be used. If this default value is too small, the
           translation sectors will become full too quickly. If this default
           value is too big, a significant part of the translation sector
           memory will be unused. Note that the average size of a basic block
           translation depends on the tool, and might depend on tool options.
           For example, the memcheck option --track-origins=yes increases the
           size of the basic block translations. Use --avg-transtab-entry-size
           to tune the size of the sectors, either to gain memory or to avoid
           too many retranslations.

       --aspace-minaddr=<address> [default: depends on the platform]
           To avoid potential conflicts with some system libraries, Valgrind
           does not use the address space below --aspace-minaddr value,
           keeping it reserved in case a library specifically requests memory
           in this region. So, some "pessimistic" value is guessed by Valgrind
           depending on the platform. On linux, by default, Valgrind avoids
           using the first 64MB even if typically there is no conflict in this
           complete zone. You can use the option --aspace-minaddr to have your
           memory hungry application benefitting from more of this lower
           memory. On the other hand, if you encounter a conflict, increasing
           aspace-minaddr value might solve it. Conflicts will typically
           manifest themselves with mmap failures in the low range of the
           address space. The provided address must be page aligned and must
           be equal or bigger to 0x1000 (4KB). To find the default value on
           your platform, do something such as valgrind -d -d date 2>&1 | grep
           -i minaddr. Values lower than 0x10000 (64KB) are known to create
           problems on some distributions.

       --valgrind-stacksize=<number> [default: 1MB]
           For each thread, Valgrind needs its own 'private' stack. The
           default size for these stacks is largely dimensioned, and so should
           be sufficient in most cases. In case the size is too small,
           Valgrind will segfault. Before segfaulting, a warning might be
           produced by Valgrind when approaching the limit.

           Use the option --valgrind-stacksize if such an (unlikely) warning
           is produced, or Valgrind dies due to a segmentation violation. Such
           segmentation violations have been seen when demangling huge C++
           symbols.

           If your application uses many threads and needs a lot of memory,
           you can gain some memory by reducing the size of these Valgrind
           stacks using the option --valgrind-stacksize.

       --show-emwarns=<yes|no> [default: no]
           When enabled, Valgrind will emit warnings about its CPU emulation
           in certain cases. These are usually not interesting.

       --require-text-symbol=:sonamepatt:fnnamepatt
           When a shared object whose soname matches sonamepatt is loaded into
           the process, examine all the text symbols it exports. If none of
           those match fnnamepatt, print an error message and abandon the run.
           This makes it possible to ensure that the run does not continue
           unless a given shared object contains a particular function name.

           Both sonamepatt and fnnamepatt can be written using the usual ?
           and * wildcards. For example: ":*libc.so*:foo?bar". You may use
           characters other than a colon to separate the two patterns. It is
           only important that the first character and the separator character
           are the same. For example, the above example could also be written
           "Q*libc.so*Qfoo?bar". Multiple
            --require-text-symbol flags are allowed, in which case shared
           objects that are loaded into the process will be checked against
           all of them.

           The purpose of this is to support reliable usage of marked-up
           libraries. For example, suppose we have a version of GCC's
           libgomp.so which has been marked up with annotations to support
           Helgrind. It is only too easy and confusing to load the wrong,
           un-annotated libgomp.so into the application. So the idea is: add a
           text symbol in the marked-up library, for example
           annotated_for_helgrind_3_6, and then give the flag
           --require-text-symbol=:*libgomp*so*:annotated_for_helgrind_3_6 so
           that when libgomp.so is loaded, Valgrind scans its symbol table,
           and if the symbol isn't present the run is aborted, rather than
           continuing silently with the un-marked-up library. Note that you
           should put the entire flag in quotes to stop shells expanding up
           the * and ?  wildcards.

       --soname-synonyms=syn1=pattern1,syn2=pattern2,...
           When a shared library is loaded, Valgrind checks for functions in
           the library that must be replaced or wrapped. For example, Memcheck
           replaces some string and memory functions (strchr, strlen, strcpy,
           memchr, memcpy, memmove, etc.) with its own versions. Such
           replacements are normally done only in shared libraries whose
           soname matches a predefined soname pattern (e.g.  libc.so* on
           linux). By default, no replacement is done for a statically linked
           binary or for alternative libraries, except for the allocation
           functions (malloc, free, calloc, memalign, realloc, operator new,
           operator delete, etc.) Such allocation functions are intercepted by
           default in any shared library or in the executable if they are
           exported as global symbols. This means that if a replacement
           allocation library such as tcmalloc is found, its functions are
           also intercepted by default. In some cases, the replacements allow
           --soname-synonyms to specify one additional synonym pattern, giving
           flexibility in the replacement. Or to prevent interception of all
           public allocation symbols.

           Currently, this flexibility is only allowed for the malloc related
           functions, using the synonym somalloc. This synonym is usable for
           all tools doing standard replacement of malloc related functions
           (e.g. memcheck, massif, drd, helgrind, exp-dhat, exp-sgcheck).

           o   Alternate malloc library: to replace the malloc related
               functions in a specific alternate library with soname
               mymalloclib.so (and not in any others), give the option
               --soname-synonyms=somalloc=mymalloclib.so. A pattern can be
               used to match multiple libraries sonames. For example,
               --soname-synonyms=somalloc=*tcmalloc* will match the soname of
               all variants of the tcmalloc library (native, debug, profiled,
               ... tcmalloc variants).

               Note: the soname of a elf shared library can be retrieved using
               the readelf utility.

           o   Replacements in a statically linked library are done by using
               the NONE pattern. For example, if you link with libtcmalloc.a,
               and only want to intercept the malloc related functions in the
               executable (and standard libraries) themselves, but not any
               other shared libraries, you can give the option
               --soname-synonyms=somalloc=NONE. Note that a NONE pattern will
               match the main executable and any shared library having no
               soname.

           o   To run a "default" Firefox build for Linux, in which JEMalloc
               is linked in to the main executable, use
               --soname-synonyms=somalloc=NONE.

           o   To only intercept allocation symbols in the default system
               libraries, but not in any other shared library or the
               executable defining public malloc or operator new related
               functions use a non-existing library name like
               --soname-synonyms=somalloc=nouserintercepts (where
               nouserintercepts can be any non-existing library name).

           o   Shared library of the dynamic (runtime) linker is excluded from
               searching for global public symbols, such as those for the
               malloc related functions (identified by somalloc synonym).

DEBUGGING VALGRIND OPTIONS
       There are also some options for debugging Valgrind itself. You
       shouldn't need to use them in the normal run of things. If you wish to
       see the list, use the --help-debug option.

MEMCHECK OPTIONS
       --leak-check=<no|summary|yes|full> [default: summary]
           When enabled, search for memory leaks when the client program
           finishes. If set to summary, it says how many leaks occurred. If
           set to full or yes, each individual leak will be shown in detail
           and/or counted as an error, as specified by the options
           --show-leak-kinds and --errors-for-leak-kinds.

       --leak-resolution=<low|med|high> [default: high]
           When doing leak checking, determines how willing Memcheck is to
           consider different backtraces to be the same for the purposes of
           merging multiple leaks into a single leak report. When set to low,
           only the first two entries need match. When med, four entries have
           to match. When high, all entries need to match.

           For hardcore leak debugging, you probably want to use
           --leak-resolution=high together with --num-callers=40 or some such
           large number.

           Note that the --leak-resolution setting does not affect Memcheck's
           ability to find leaks. It only changes how the results are
           presented.

       --show-leak-kinds=<set> [default: definite,possible]
           Specifies the leak kinds to show in a full leak search, in one of
           the following ways:

           o   a comma separated list of one or more of definite indirect
               possible reachable.

           o   all to specify the complete set (all leak kinds). It is
               equivalent to
               --show-leak-kinds=definite,indirect,possible,reachable.

           o   none for the empty set.

       --errors-for-leak-kinds=<set> [default: definite,possible]
           Specifies the leak kinds to count as errors in a full leak search.
           The <set> is specified similarly to --show-leak-kinds

       --leak-check-heuristics=<set> [default: all]
           Specifies the set of leak check heuristics to be used during leak
           searches. The heuristics control which interior pointers to a block
           cause it to be considered as reachable. The heuristic set is
           specified in one of the following ways:

           o   a comma separated list of one or more of stdstring length64
               newarray multipleinheritance.

           o   all to activate the complete set of heuristics. It is
               equivalent to
               --leak-check-heuristics=stdstring,length64,newarray,multipleinheritance.

           o   none for the empty set.

           Note that these heuristics are dependent on the layout of the
           objects produced by the C++ compiler. They have been tested with
           some gcc versions (e.g. 4.4 and 4.7). They might not work properly
           with other C++ compilers.

       --show-reachable=<yes|no> , --show-possibly-lost=<yes|no>
           These options provide an alternative way to specify the leak kinds
           to show:

           o   --show-reachable=no --show-possibly-lost=yes is equivalent to
               --show-leak-kinds=definite,possible.

           o   --show-reachable=no --show-possibly-lost=no is equivalent to
               --show-leak-kinds=definite.

           o   --show-reachable=yes is equivalent to --show-leak-kinds=all.

           Note that --show-possibly-lost=no has no effect if
           --show-reachable=yes is specified.

       --xtree-leak=<no|yes> [no]
           If set to yes, the results for the leak search done at exit will be
           output in a 'Callgrind Format' execution tree file. Note that this
           automatically sets the option --leak-check=full. The produced file
           will contain the following events:

           o   RB : Reachable Bytes

           o   PB : Possibly lost Bytes

           o   IB : Indirectly lost Bytes

           o   DB : Definitely lost Bytes (direct plus indirect)

           o   DIB : Definitely Indirectly lost Bytes (subset of DB)

           o   RBk : reachable Blocks

           o   PBk : Possibly lost Blocks

           o   IBk : Indirectly lost Blocks

           o   DBk : Definitely lost Blocks

           The increase or decrease for all events above will also be output
           in the file to provide the delta (increase or decreasea between 2
           successive leak searches. For example, iRB is the increase of the
           RB event, dPBk is the decrease of PBk event. The values for the
           increase and decrease events will be zero for the first leak search
           done.

           See ???  for a detailed explanation about execution trees.

       --xtree-leak-file=<filename> [default: xtleak.kcg.%p]
           Specifies that Valgrind should produce the xtree leak report in the
           specified file. Any %p, %q or %n sequences appearing in the
           filename are expanded in exactly the same way as they are for
           --log-file. See the description of --log-file for details.

           See ???  for a detailed explanation about execution trees formats.

       --undef-value-errors=<yes|no> [default: yes]
           Controls whether Memcheck reports uses of undefined value errors.
           Set this to no if you don't want to see undefined value errors. It
           also has the side effect of speeding up Memcheck somewhat.

       --track-origins=<yes|no> [default: no]
           Controls whether Memcheck tracks the origin of uninitialised
           values. By default, it does not, which means that although it can
           tell you that an uninitialised value is being used in a dangerous
           way, it cannot tell you where the uninitialised value came from.
           This often makes it difficult to track down the root problem.

           When set to yes, Memcheck keeps track of the origins of all
           uninitialised values. Then, when an uninitialised value error is
           reported, Memcheck will try to show the origin of the value. An
           origin can be one of the following four places: a heap block, a
           stack allocation, a client request, or miscellaneous other sources
           (eg, a call to brk).

           For uninitialised values originating from a heap block, Memcheck
           shows where the block was allocated. For uninitialised values
           originating from a stack allocation, Memcheck can tell you which
           function allocated the value, but no more than that -- typically it
           shows you the source location of the opening brace of the function.
           So you should carefully check that all of the function's local
           variables are initialised properly.

           Performance overhead: origin tracking is expensive. It halves
           Memcheck's speed and increases memory use by a minimum of 100MB,
           and possibly more. Nevertheless it can drastically reduce the
           effort required to identify the root cause of uninitialised value
           errors, and so is often a programmer productivity win, despite
           running more slowly.

           Accuracy: Memcheck tracks origins quite accurately. To avoid very
           large space and time overheads, some approximations are made. It is
           possible, although unlikely, that Memcheck will report an incorrect
           origin, or not be able to identify any origin.

           Note that the combination --track-origins=yes and
           --undef-value-errors=no is nonsensical. Memcheck checks for and
           rejects this combination at startup.

       --partial-loads-ok=<yes|no> [default: yes]
           Controls how Memcheck handles 32-, 64-, 128- and 256-bit naturally
           aligned loads from addresses for which some bytes are addressable
           and others are not. When yes, such loads do not produce an address
           error. Instead, loaded bytes originating from illegal addresses are
           marked as uninitialised, and those corresponding to legal addresses
           are handled in the normal way.

           When no, loads from partially invalid addresses are treated the
           same as loads from completely invalid addresses: an illegal-address
           error is issued, and the resulting bytes are marked as initialised.

           Note that code that behaves in this way is in violation of the ISO
           C/C++ standards, and should be considered broken. If at all
           possible, such code should be fixed.

       --expensive-definedness-checks=<yes|no> [default: no]
           Controls whether Memcheck should employ more precise but also more
           expensive (time consuming) algorithms when checking the definedness
           of a value. The default setting is not to do that and it is usually
           sufficient. However, for highly optimised code valgrind may
           sometimes incorrectly complain. Invoking valgrind with
           --expensive-definedness-checks=yes helps but comes at a performance
           cost. Runtime degradation of 25% have been observed but the extra
           cost depends a lot on the application at hand.

       --keep-stacktraces=alloc|free|alloc-and-free|alloc-then-free|none
       [default: alloc-and-free]
           Controls which stack trace(s) to keep for malloc'd and/or free'd
           blocks.

           With alloc-then-free, a stack trace is recorded at allocation time,
           and is associated with the block. When the block is freed, a second
           stack trace is recorded, and this replaces the allocation stack
           trace. As a result, any "use after free" errors relating to this
           block can only show a stack trace for where the block was freed.

           With alloc-and-free, both allocation and the deallocation stack
           traces for the block are stored. Hence a "use after free" error
           will show both, which may make the error easier to diagnose.
           Compared to alloc-then-free, this setting slightly increases
           Valgrind's memory use as the block contains two references instead
           of one.

           With alloc, only the allocation stack trace is recorded (and
           reported). With free, only the deallocation stack trace is recorded
           (and reported). These values somewhat decrease Valgrind's memory
           and cpu usage. They can be useful depending on the error types you
           are searching for and the level of detail you need to analyse them.
           For example, if you are only interested in memory leak errors, it
           is sufficient to record the allocation stack traces.

           With none, no stack traces are recorded for malloc and free
           operations. If your program allocates a lot of blocks and/or
           allocates/frees from many different stack traces, this can
           significantly decrease cpu and/or memory required. Of course, few
           details will be reported for errors related to heap blocks.

           Note that once a stack trace is recorded, Valgrind keeps the stack
           trace in memory even if it is not referenced by any block. Some
           programs (for example, recursive algorithms) can generate a huge
           number of stack traces. If Valgrind uses too much memory in such
           circumstances, you can reduce the memory required with the options
           --keep-stacktraces and/or by using a smaller value for the option
           --num-callers.

           If you want to use --xtree-memory=full memory profiling (see ???
           ), then you cannot specify --keep-stacktraces=free or
           --keep-stacktraces=none.

       --freelist-vol=<number> [default: 20000000]
           When the client program releases memory using free (in C) or delete
           (C++), that memory is not immediately made available for
           re-allocation. Instead, it is marked inaccessible and placed in a
           queue of freed blocks. The purpose is to defer as long as possible
           the point at which freed-up memory comes back into circulation.
           This increases the chance that Memcheck will be able to detect
           invalid accesses to blocks for some significant period of time
           after they have been freed.

           This option specifies the maximum total size, in bytes, of the
           blocks in the queue. The default value is twenty million bytes.
           Increasing this increases the total amount of memory used by
           Memcheck but may detect invalid uses of freed blocks which would
           otherwise go undetected.

       --freelist-big-blocks=<number> [default: 1000000]
           When making blocks from the queue of freed blocks available for
           re-allocation, Memcheck will in priority re-circulate the blocks
           with a size greater or equal to --freelist-big-blocks. This ensures
           that freeing big blocks (in particular freeing blocks bigger than
           --freelist-vol) does not immediately lead to a re-circulation of
           all (or a lot of) the small blocks in the free list. In other
           words, this option increases the likelihood to discover dangling
           pointers for the "small" blocks, even when big blocks are freed.

           Setting a value of 0 means that all the blocks are re-circulated in
           a FIFO order.

       --workaround-gcc296-bugs=<yes|no> [default: no]
           When enabled, assume that reads and writes some small distance
           below the stack pointer are due to bugs in GCC 2.96, and does not
           report them. The "small distance" is 256 bytes by default. Note
           that GCC 2.96 is the default compiler on some ancient Linux
           distributions (RedHat 7.X) and so you may need to use this option.
           Do not use it if you do not have to, as it can cause real errors to
           be overlooked. A better alternative is to use a more recent GCC in
           which this bug is fixed.

           You may also need to use this option when working with GCC 3.X or
           4.X on 32-bit PowerPC Linux. This is because GCC generates code
           which occasionally accesses below the stack pointer, particularly
           for floating-point to/from integer conversions. This is in
           violation of the 32-bit PowerPC ELF specification, which makes no
           provision for locations below the stack pointer to be accessible.

           This option is deprecated as of version 3.12 and may be removed
           from future versions. You should instead use
           --ignore-range-below-sp to specify the exact range of offsets below
           the stack pointer that should be ignored. A suitable equivalent is
           --ignore-range-below-sp=1024-1.

       --ignore-range-below-sp=<number>-<number>
           This is a more general replacement for the deprecated
           --workaround-gcc296-bugs option. When specified, it causes Memcheck
           not to report errors for accesses at the specified offsets below
           the stack pointer. The two offsets must be positive decimal numbers
           and -- somewhat counterintuitively -- the first one must be larger,
           in order to imply a non-wraparound address range to ignore. For
           example, to ignore 4 byte accesses at 8192 bytes below the stack
           pointer, use --ignore-range-below-sp=8192-8189. Only one range may
           be specified.

       --show-mismatched-frees=<yes|no> [default: yes]
           When enabled, Memcheck checks that heap blocks are deallocated
           using a function that matches the allocating function. That is, it
           expects free to be used to deallocate blocks allocated by malloc,
           delete for blocks allocated by new, and delete[] for blocks
           allocated by new[]. If a mismatch is detected, an error is
           reported. This is in general important because in some
           environments, freeing with a non-matching function can cause
           crashes.

           There is however a scenario where such mismatches cannot be
           avoided. That is when the user provides implementations of
           new/new[] that call malloc and of delete/delete[] that call free,
           and these functions are asymmetrically inlined. For example,
           imagine that delete[] is inlined but new[] is not. The result is
           that Memcheck "sees" all delete[] calls as direct calls to free,
           even when the program source contains no mismatched calls.

           This causes a lot of confusing and irrelevant error reports.
           --show-mismatched-frees=no disables these checks. It is not
           generally advisable to disable them, though, because you may miss
           real errors as a result.

       --ignore-ranges=0xPP-0xQQ[,0xRR-0xSS]
           Any ranges listed in this option (and multiple ranges can be
           specified, separated by commas) will be ignored by Memcheck's
           addressability checking.

       --malloc-fill=<hexnumber>
           Fills blocks allocated by malloc, new, etc, but not by calloc, with
           the specified byte. This can be useful when trying to shake out
           obscure memory corruption problems. The allocated area is still
           regarded by Memcheck as undefined -- this option only affects its
           contents. Note that --malloc-fill does not affect a block of memory
           when it is used as argument to client requests
           VALGRIND_MEMPOOL_ALLOC or VALGRIND_MALLOCLIKE_BLOCK.

       --free-fill=<hexnumber>
           Fills blocks freed by free, delete, etc, with the specified byte
           value. This can be useful when trying to shake out obscure memory
           corruption problems. The freed area is still regarded by Memcheck
           as not valid for access -- this option only affects its contents.
           Note that --free-fill does not affect a block of memory when it is
           used as argument to client requests VALGRIND_MEMPOOL_FREE or
           VALGRIND_FREELIKE_BLOCK.

CACHEGRIND OPTIONS
       --I1=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the level 1
           instruction cache.

       --D1=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the level 1 data
           cache.

       --LL=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the last-level
           cache.

       --cache-sim=no|yes [yes]
           Enables or disables collection of cache access and miss counts.

       --branch-sim=no|yes [no]
           Enables or disables collection of branch instruction and
           misprediction counts. By default this is disabled as it slows
           Cachegrind down by approximately 25%. Note that you cannot specify
           --cache-sim=no and --branch-sim=no together, as that would leave
           Cachegrind with no information to collect.

       --cachegrind-out-file=<file>
           Write the profile data to file rather than to the default output
           file, cachegrind.out.<pid>. The %p and %q format specifiers can be
           used to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-
           file.

CALLGRIND OPTIONS
       --callgrind-out-file=<file>
           Write the profile data to file rather than to the default output
           file, callgrind.out.<pid>. The %p and %q format specifiers can be
           used to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-
           file. When multiple dumps are made, the file name is modified
           further; see below.

       --dump-line=<no|yes> [default: yes]
           This specifies that event counting should be performed at source
           line granularity. This allows source annotation for sources which
           are compiled with debug information (-g).

       --dump-instr=<no|yes> [default: no]
           This specifies that event counting should be performed at
           per-instruction granularity. This allows for assembly code
           annotation. Currently the results can only be displayed by
           KCachegrind.

       --compress-strings=<no|yes> [default: yes]
           This option influences the output format of the profile data. It
           specifies whether strings (file and function names) should be
           identified by numbers. This shrinks the file, but makes it more
           difficult for humans to read (which is not recommended in any
           case).

       --compress-pos=<no|yes> [default: yes]
           This option influences the output format of the profile data. It
           specifies whether numerical positions are always specified as
           absolute values or are allowed to be relative to previous numbers.
           This shrinks the file size.

       --combine-dumps=<no|yes> [default: no]
           When enabled, when multiple profile data parts are to be generated
           these parts are appended to the same output file. Not recommended.

       --dump-every-bb=<count> [default: 0, never]
           Dump profile data every count basic blocks. Whether a dump is
           needed is only checked when Valgrind's internal scheduler is run.
           Therefore, the minimum setting useful is about 100000. The count is
           a 64-bit value to make long dump periods possible.

       --dump-before=<function>
           Dump when entering function.

       --zero-before=<function>
           Zero all costs when entering function.

       --dump-after=<function>
           Dump when leaving function.

       --instr-atstart=<yes|no> [default: yes]
           Specify if you want Callgrind to start simulation and profiling
           from the beginning of the program. When set to no, Callgrind will
           not be able to collect any information, including calls, but it
           will have at most a slowdown of around 4, which is the minimum
           Valgrind overhead. Instrumentation can be interactively enabled via
           callgrind_control -i on.

           Note that the resulting call graph will most probably not contain
           main, but will contain all the functions executed after
           instrumentation was enabled. Instrumentation can also
           programatically enabled/disabled. See the Callgrind include file
           callgrind.h for the macro you have to use in your source code.

           For cache simulation, results will be less accurate when switching
           on instrumentation later in the program run, as the simulator
           starts with an empty cache at that moment. Switch on event
           collection later to cope with this error.

       --collect-atstart=<yes|no> [default: yes]
           Specify whether event collection is enabled at beginning of the
           profile run.

           To only look at parts of your program, you have two possibilities:

            1. Zero event counters before entering the program part you want
               to profile, and dump the event counters to a file after leaving
               that program part.

            2. Switch on/off collection state as needed to only see event
               counters happening while inside of the program part you want to
               profile.

           The second option can be used if the program part you want to
           profile is called many times. Option 1, i.e. creating a lot of
           dumps is not practical here.

           Collection state can be toggled at entry and exit of a given
           function with the option --toggle-collect. If you use this option,
           collection state should be disabled at the beginning. Note that the
           specification of --toggle-collect implicitly sets
           --collect-state=no.

           Collection state can be toggled also by inserting the client
           request CALLGRIND_TOGGLE_COLLECT ; at the needed code positions.

       --toggle-collect=<function>
           Toggle collection on entry/exit of function.

       --collect-jumps=<no|yes> [default: no]
           This specifies whether information for (conditional) jumps should
           be collected. As above, callgrind_annotate currently is not able to
           show you the data. You have to use KCachegrind to get jump arrows
           in the annotated code.

       --collect-systime=<no|yes> [default: no]
           This specifies whether information for system call times should be
           collected.

       --collect-bus=<no|yes> [default: no]
           This specifies whether the number of global bus events executed
           should be collected. The event type "Ge" is used for these events.

       --cache-sim=<yes|no> [default: no]
           Specify if you want to do full cache simulation. By default, only
           instruction read accesses will be counted ("Ir"). With cache
           simulation, further event counters are enabled: Cache misses on
           instruction reads ("I1mr"/"ILmr"), data read accesses ("Dr") and
           related cache misses ("D1mr"/"DLmr"), data write accesses ("Dw")
           and related cache misses ("D1mw"/"DLmw"). For more information, see
           Cachegrind: a cache and branch-prediction profiler.

       --branch-sim=<yes|no> [default: no]
           Specify if you want to do branch prediction simulation. Further
           event counters are enabled: Number of executed conditional branches
           and related predictor misses ("Bc"/"Bcm"), executed indirect jumps
           and related misses of the jump address predictor ("Bi"/"Bim").

HELGRIND OPTIONS
       --free-is-write=no|yes [default: no]
           When enabled (not the default), Helgrind treats freeing of heap
           memory as if the memory was written immediately before the free.
           This exposes races where memory is referenced by one thread, and
           freed by another, but there is no observable synchronisation event
           to ensure that the reference happens before the free.

           This functionality is new in Valgrind 3.7.0, and is regarded as
           experimental. It is not enabled by default because its interaction
           with custom memory allocators is not well understood at present.
           User feedback is welcomed.

       --track-lockorders=no|yes [default: yes]
           When enabled (the default), Helgrind performs lock order
           consistency checking. For some buggy programs, the large number of
           lock order errors reported can become annoying, particularly if
           you're only interested in race errors. You may therefore find it
           helpful to disable lock order checking.

       --history-level=none|approx|full [default: full]
           --history-level=full (the default) causes Helgrind collects enough
           information about "old" accesses that it can produce two stack
           traces in a race report -- both the stack trace for the current
           access, and the trace for the older, conflicting access. To limit
           memory usage, "old" accesses stack traces are limited to a maximum
           of 8 entries, even if --num-callers value is bigger.

           Collecting such information is expensive in both speed and memory,
           particularly for programs that do many inter-thread synchronisation
           events (locks, unlocks, etc). Without such information, it is more
           difficult to track down the root causes of races. Nonetheless, you
           may not need it in situations where you just want to check for the
           presence or absence of races, for example, when doing regression
           testing of a previously race-free program.

           --history-level=none is the opposite extreme. It causes Helgrind
           not to collect any information about previous accesses. This can be
           dramatically faster than --history-level=full.

           --history-level=approx provides a compromise between these two
           extremes. It causes Helgrind to show a full trace for the later
           access, and approximate information regarding the earlier access.
           This approximate information consists of two stacks, and the
           earlier access is guaranteed to have occurred somewhere between
           program points denoted by the two stacks. This is not as useful as
           showing the exact stack for the previous access (as
           --history-level=full does), but it is better than nothing, and it
           is almost as fast as --history-level=none.

       --conflict-cache-size=N [default: 1000000]
           This flag only has any effect at --history-level=full.

           Information about "old" conflicting accesses is stored in a cache
           of limited size, with LRU-style management. This is necessary
           because it isn't practical to store a stack trace for every single
           memory access made by the program. Historical information on not
           recently accessed locations is periodically discarded, to free up
           space in the cache.

           This option controls the size of the cache, in terms of the number
           of different memory addresses for which conflicting access
           information is stored. If you find that Helgrind is showing race
           errors with only one stack instead of the expected two stacks, try
           increasing this value.

           The minimum value is 10,000 and the maximum is 30,000,000 (thirty
           times the default value). Increasing the value by 1 increases
           Helgrind's memory requirement by very roughly 100 bytes, so the
           maximum value will easily eat up three extra gigabytes or so of
           memory.

       --check-stack-refs=no|yes [default: yes]
           By default Helgrind checks all data memory accesses made by your
           program. This flag enables you to skip checking for accesses to
           thread stacks (local variables). This can improve performance, but
           comes at the cost of missing races on stack-allocated data.

       --ignore-thread-creation=<yes|no> [default: no]
           Controls whether all activities during thread creation should be
           ignored. By default enabled only on Solaris. Solaris provides
           higher throughput, parallelism and scalability than other operating
           systems, at the cost of more fine-grained locking activity. This
           means for example that when a thread is created under glibc, just
           one big lock is used for all thread setup. Solaris libc uses
           several fine-grained locks and the creator thread resumes its
           activities as soon as possible, leaving for example stack and TLS
           setup sequence to the created thread. This situation confuses
           Helgrind as it assumes there is some false ordering in place
           between creator and created thread; and therefore many types of
           race conditions in the application would not be reported. To
           prevent such false ordering, this command line option is set to yes
           by default on Solaris. All activity (loads, stores, client
           requests) is therefore ignored during:

           o   pthread_create() call in the creator thread

           o   thread creation phase (stack and TLS setup) in the created
               thread

           Also new memory allocated during thread creation is untracked, that
           is race reporting is suppressed there. DRD does the same thing
           implicitly. This is necessary because Solaris libc caches many
           objects and reuses them for different threads and that confuses
           Helgrind.

DRD OPTIONS
       --check-stack-var=<yes|no> [default: no]
           Controls whether DRD detects data races on stack variables.
           Verifying stack variables is disabled by default because most
           programs do not share stack variables over threads.

       --exclusive-threshold=<n> [default: off]
           Print an error message if any mutex or writer lock has been held
           longer than the time specified in milliseconds. This option enables
           the detection of lock contention.

       --join-list-vol=<n> [default: 10]
           Data races that occur between a statement at the end of one thread
           and another thread can be missed if memory access information is
           discarded immediately after a thread has been joined. This option
           allows one to specify for how many joined threads memory access
           information should be retained.

        --first-race-only=<yes|no> [default: no]
           Whether to report only the first data race that has been detected
           on a memory location or all data races that have been detected on a
           memory location.

        --free-is-write=<yes|no> [default: no]
           Whether to report races between accessing memory and freeing
           memory. Enabling this option may cause DRD to run slightly slower.
           Notes:

           o   Don't enable this option when using custom memory allocators
               that use the VG_USERREQ__MALLOCLIKE_BLOCK and
               VG_USERREQ__FREELIKE_BLOCK because that would result in false
               positives.

           o   Don't enable this option when using reference-counted objects
               because that will result in false positives, even when that
               code has been annotated properly with ANNOTATE_HAPPENS_BEFORE
               and ANNOTATE_HAPPENS_AFTER. See e.g. the output of the
               following command for an example: valgrind --tool=drd
               --free-is-write=yes drd/tests/annotate_smart_pointer.

        --report-signal-unlocked=<yes|no> [default: yes]
           Whether to report calls to pthread_cond_signal and
           pthread_cond_broadcast where the mutex associated with the signal
           through pthread_cond_wait or pthread_cond_timed_waitis not locked
           at the time the signal is sent. Sending a signal without holding a
           lock on the associated mutex is a common programming error which
           can cause subtle race conditions and unpredictable behavior. There
           exist some uncommon synchronization patterns however where it is
           safe to send a signal without holding a lock on the associated
           mutex.

       --segment-merging=<yes|no> [default: yes]
           Controls segment merging. Segment merging is an algorithm to limit
           memory usage of the data race detection algorithm. Disabling
           segment merging may improve the accuracy of the so-called 'other
           segments' displayed in race reports but can also trigger an out of
           memory error.

       --segment-merging-interval=<n> [default: 10]
           Perform segment merging only after the specified number of new
           segments have been created. This is an advanced configuration
           option that allows one to choose whether to minimize DRD's memory
           usage by choosing a low value or to let DRD run faster by choosing
           a slightly higher value. The optimal value for this parameter
           depends on the program being analyzed. The default value works well
           for most programs.

       --shared-threshold=<n> [default: off]
           Print an error message if a reader lock has been held longer than
           the specified time (in milliseconds). This option enables the
           detection of lock contention.

       --show-confl-seg=<yes|no> [default: yes]
           Show conflicting segments in race reports. Since this information
           can help to find the cause of a data race, this option is enabled
           by default. Disabling this option makes the output of DRD more
           compact.

       --show-stack-usage=<yes|no> [default: no]
           Print stack usage at thread exit time. When a program creates a
           large number of threads it becomes important to limit the amount of
           virtual memory allocated for thread stacks. This option makes it
           possible to observe how much stack memory has been used by each
           thread of the client program. Note: the DRD tool itself allocates
           some temporary data on the client thread stack. The space necessary
           for this temporary data must be allocated by the client program
           when it allocates stack memory, but is not included in stack usage
           reported by DRD.

       --ignore-thread-creation=<yes|no> [default: no]
           Controls whether all activities during thread creation should be
           ignored. By default enabled only on Solaris. Solaris provides
           higher throughput, parallelism and scalability than other operating
           systems, at the cost of more fine-grained locking activity. This
           means for example that when a thread is created under glibc, just
           one big lock is used for all thread setup. Solaris libc uses
           several fine-grained locks and the creator thread resumes its
           activities as soon as possible, leaving for example stack and TLS
           setup sequence to the created thread. This situation confuses DRD
           as it assumes there is some false ordering in place between creator
           and created thread; and therefore many types of race conditions in
           the application would not be reported. To prevent such false
           ordering, this command line option is set to yes by default on
           Solaris. All activity (loads, stores, client requests) is therefore
           ignored during:

           o   pthread_create() call in the creator thread

           o   thread creation phase (stack and TLS setup) in the created
               thread

       --trace-addr=<address> [default: none]
           Trace all load and store activity for the specified address. This
           option may be specified more than once.

       --ptrace-addr=<address> [default: none]
           Trace all load and store activity for the specified address and
           keep doing that even after the memory at that address has been
           freed and reallocated.

       --trace-alloc=<yes|no> [default: no]
           Trace all memory allocations and deallocations. May produce a huge
           amount of output.

       --trace-barrier=<yes|no> [default: no]
           Trace all barrier activity.

       --trace-cond=<yes|no> [default: no]
           Trace all condition variable activity.

       --trace-fork-join=<yes|no> [default: no]
           Trace all thread creation and all thread termination events.

       --trace-hb=<yes|no> [default: no]
           Trace execution of the ANNOTATE_HAPPENS_BEFORE(),
           ANNOTATE_HAPPENS_AFTER() and ANNOTATE_HAPPENS_DONE() client
           requests.

       --trace-mutex=<yes|no> [default: no]
           Trace all mutex activity.

       --trace-rwlock=<yes|no> [default: no]
           Trace all reader-writer lock activity.

       --trace-semaphore=<yes|no> [default: no]
           Trace all semaphore activity.

MASSIF OPTIONS
       --heap=<yes|no> [default: yes]
           Specifies whether heap profiling should be done.

       --heap-admin=<size> [default: 8]
           If heap profiling is enabled, gives the number of administrative
           bytes per block to use. This should be an estimate of the average,
           since it may vary. For example, the allocator used by glibc on
           Linux requires somewhere between 4 to 15 bytes per block, depending
           on various factors. That allocator also requires admin space for
           freed blocks, but Massif cannot account for this.

       --stacks=<yes|no> [default: no]
           Specifies whether stack profiling should be done. This option slows
           Massif down greatly, and so is off by default. Note that Massif
           assumes that the main stack has size zero at start-up. This is not
           true, but doing otherwise accurately is difficult. Furthermore,
           starting at zero better indicates the size of the part of the main
           stack that a user program actually has control over.

       --pages-as-heap=<yes|no> [default: no]
           Tells Massif to profile memory at the page level rather than at the
           malloc'd block level. See above for details.

       --depth=<number> [default: 30]
           Maximum depth of the allocation trees recorded for detailed
           snapshots. Increasing it will make Massif run somewhat more slowly,
           use more memory, and produce bigger output files.

       --alloc-fn=<name>
           Functions specified with this option will be treated as though they
           were a heap allocation function such as malloc. This is useful for
           functions that are wrappers to malloc or new, which can fill up the
           allocation trees with uninteresting information. This option can be
           specified multiple times on the command line, to name multiple
           functions.

           Note that the named function will only be treated this way if it is
           the top entry in a stack trace, or just below another function
           treated this way. For example, if you have a function malloc1 that
           wraps malloc, and malloc2 that wraps malloc1, just specifying
           --alloc-fn=malloc2 will have no effect. You need to specify
           --alloc-fn=malloc1 as well. This is a little inconvenient, but the
           reason is that checking for allocation functions is slow, and it
           saves a lot of time if Massif can stop looking through the stack
           trace entries as soon as it finds one that doesn't match rather
           than having to continue through all the entries.

           Note that C++ names are demangled. Note also that overloaded C++
           names must be written in full. Single quotes may be necessary to
           prevent the shell from breaking them up. For example:

               --alloc-fn='operator new(unsigned, std::nothrow_t const&)'

       --ignore-fn=<name>
           Any direct heap allocation (i.e. a call to malloc, new, etc, or a
           call to a function named by an --alloc-fn option) that occurs in a
           function specified by this option will be ignored. This is mostly
           useful for testing purposes. This option can be specified multiple
           times on the command line, to name multiple functions.

           Any realloc of an ignored block will also be ignored, even if the
           realloc call does not occur in an ignored function. This avoids the
           possibility of negative heap sizes if ignored blocks are shrunk
           with realloc.

           The rules for writing C++ function names are the same as for
           --alloc-fn above.

       --threshold=<m.n> [default: 1.0]
           The significance threshold for heap allocations, as a percentage of
           total memory size. Allocation tree entries that account for less
           than this will be aggregated. Note that this should be specified in
           tandem with ms_print's option of the same name.

       --peak-inaccuracy=<m.n> [default: 1.0]
           Massif does not necessarily record the actual global memory
           allocation peak; by default it records a peak only when the global
           memory allocation size exceeds the previous peak by at least 1.0%.
           This is because there can be many local allocation peaks along the
           way, and doing a detailed snapshot for every one would be expensive
           and wasteful, as all but one of them will be later discarded. This
           inaccuracy can be changed (even to 0.0%) via this option, but
           Massif will run drastically slower as the number approaches zero.

       --time-unit=<i|ms|B> [default: i]
           The time unit used for the profiling. There are three
           possibilities: instructions executed (i), which is good for most
           cases; real (wallclock) time (ms, i.e. milliseconds), which is
           sometimes useful; and bytes allocated/deallocated on the heap
           and/or stack (B), which is useful for very short-run programs, and
           for testing purposes, because it is the most reproducible across
           different machines.

       --detailed-freq=<n> [default: 10]
           Frequency of detailed snapshots. With --detailed-freq=1, every
           snapshot is detailed.

       --max-snapshots=<n> [default: 100]
           The maximum number of snapshots recorded. If set to N, for all
           programs except very short-running ones, the final number of
           snapshots will be between N/2 and N.

       --massif-out-file=<file> [default: massif.out.%p]
           Write the profile data to file rather than to the default output
           file, massif.out.<pid>. The %p and %q format specifiers can be used
           to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-
           file.

SGCHECK OPTIONS
       There are no SGCheck-specific command-line options at present.

BBV OPTIONS
       --bb-out-file=<name> [default: bb.out.%p]
           This option selects the name of the basic block vector file. The %p
           and %q format specifiers can be used to embed the process ID and/or
           the contents of an environment variable in the name, as is the case
           for the core option --log-file.

       --pc-out-file=<name> [default: pc.out.%p]
           This option selects the name of the PC file. This file holds
           program counter addresses and function name info for the various
           basic blocks. This can be used in conjunction with the basic block
           vector file to fast-forward via function names instead of just
           instruction counts. The %p and %q format specifiers can be used to
           embed the process ID and/or the contents of an environment variable
           in the name, as is the case for the core option --log-file.

       --interval-size=<number> [default: 100000000]
           This option selects the size of the interval to use. The default is
           100 million instructions, which is a commonly used value. Other
           sizes can be used; smaller intervals can help programs with
           finer-grained phases. However smaller interval size can lead to
           accuracy issues due to warm-up effects (When fast-forwarding the
           various architectural features will be un-initialized, and it will
           take some number of instructions before they "warm up" to the state
           a full simulation would be at without the fast-forwarding. Large
           interval sizes tend to mitigate this.)

       --instr-count-only [default: no]
           This option tells the tool to only display instruction count
           totals, and to not generate the actual basic block vector file.
           This is useful for debugging, and for gathering instruction count
           info without generating the large basic block vector files.

LACKEY OPTIONS
       --basic-counts=<no|yes> [default: yes]
           When enabled, Lackey prints the following statistics and
           information about the execution of the client program:

            1. The number of calls to the function specified by the --fnname
               option (the default is main). If the program has had its
               symbols stripped, the count will always be zero.

            2. The number of conditional branches encountered and the number
               and proportion of those taken.

            3. The number of superblocks entered and completed by the program.
               Note that due to optimisations done by the JIT, this is not at
               all an accurate value.

            4. The number of guest (x86, amd64, ppc, etc.) instructions and IR
               statements executed. IR is Valgrind's RISC-like intermediate
               representation via which all instrumentation is done.

            5. Ratios between some of these counts.

            6. The exit code of the client program.

       --detailed-counts=<no|yes> [default: no]
           When enabled, Lackey prints a table containing counts of loads,
           stores and ALU operations, differentiated by their IR types. The IR
           types are identified by their IR name ("I1", "I8", ... "I128",
           "F32", "F64", and "V128").

       --trace-mem=<no|yes> [default: no]
           When enabled, Lackey prints the size and address of almost every
           memory access made by the program. See the comments at the top of
           the file lackey/lk_main.c for details about the output format, how
           it works, and inaccuracies in the address trace. Note that this
           option produces immense amounts of output.

       --trace-superblocks=<no|yes> [default: no]
           When enabled, Lackey prints out the address of every superblock (a
           single entry, multiple exit, linear chunk of code) executed by the
           program. This is primarily of interest to Valgrind developers. See
           the comments at the top of the file lackey/lk_main.c for details
           about the output format. Note that this option produces large
           amounts of output.

       --fnname=<name> [default: main]
           Changes the function for which calls are counted when
           --basic-counts=yes is specified.

SEE ALSO
       cg_annotate(1), callgrind_annotate(1), callgrind_control(1),
       ms_print(1), $INSTALL/share/doc/valgrind/html/index.html or
       http://www.valgrind.org/docs/manual/index.html, Debugging your program
       using Valgrind's gdbserver and GDB[1] vgdb[2], Valgrind monitor
       commands[3], The Commentary[4], Scheduling and Multi-Thread
       Performance[5], Cachegrind: a cache and branch-prediction profiler[6].

AUTHOR
       See the AUTHORS file in the valgrind distribution for a comprehensive
       list of authors.

       This manpage was written by Andres Roldan <aroldan@debian.org> and the
       Valgrind developers.

NOTES
        1. Debugging your program using Valgrind's gdbserver and GDB
           http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.gdbserver

        2. vgdb
           http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.vgdb

        3. Valgrind monitor commands
           http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.valgrind-monitor-commands

        4. The Commentary
           http://www.valgrind.org/docs/manual/manual-core.html#manual-core.comment

        5. Scheduling and Multi-Thread Performance
           http://www.valgrind.org/docs/manual/manual-core.html#manual-core.pthreads_perf_sched

        6. Cachegrind: a cache and branch-prediction profiler
           http://www.valgrind.org/docs/manual/cg-manual.html

Release 3.13.0                    04/15/2018                       VALGRIND(1)

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