LLVM-COV(1) LLVM LLVM-COV(1)
llvm-cov - emit coverage information
llvm-cov [options] SOURCEFILE
The llvm-cov tool reads code coverage data files and displays the cov-
erage information for a specified source file. It is compatible with
the gcov tool from version 4.2 of GCC and may also be compatible with
some later versions of gcov.
To use llvm-cov, you must first build an instrumented version of your
application that collects coverage data as it runs. Compile with the
-fprofile-arcs and -ftest-coverage options to add the instrumentation.
(Alternatively, you can use the --coverage option, which includes both
of those other options.) You should compile with debugging information
(-g) and without optimization (-O0); otherwise, the coverage data can-
not be accurately mapped back to the source code.
At the time you compile the instrumented code, a .gcno data file will
be generated for each object file. These .gcno files contain half of
the coverage data. The other half of the data comes from .gcda files
that are generated when you run the instrumented program, with a sepa-
rate .gcda file for each object file. Each time you run the program,
the execution counts are summed into any existing .gcda files, so be
sure to remove any old files if you do not want their contents to be
By default, the .gcda files are written into the same directory as the
object files, but you can override that by setting the GCOV_PREFIX and
GCOV_PREFIX_STRIP environment variables. The GCOV_PREFIX_STRIP variable
specifies a number of directory components to be removed from the start
of the absolute path to the object file directory. After stripping
those directories, the prefix from the GCOV_PREFIX variable is added.
These environment variables allow you to run the instrumented program
on a machine where the original object file directories are not acces-
sible, but you will then need to copy the .gcda files back to the ob-
ject file directories where llvm-cov expects to find them.
Once you have generated the coverage data files, run llvm-cov for each
main source file where you want to examine the coverage results. This
should be run from the same directory where you previously ran the com-
piler. The results for the specified source file are written to a file
named by appending a .gcov suffix. A separate output file is also cre-
ated for each file included by the main source file, also with a .gcov
The basic content of an llvm-cov output file is a copy of the source
file with an execution count and line number prepended to every line.
The execution count is shown as - if a line does not contain any exe-
cutable code. If a line contains code but that code was never executed,
the count is displayed as #####.
Display all basic blocks. If there are multiple blocks for a
single line of source code, this option causes llvm-cov to show
the count for each block instead of just one count for the en-
Display conditional branch probabilities and a summary of branch
Display branch counts instead of probabilities (requires -b).
Show a summary of coverage for each function instead of just one
summary for an entire source file.
--help Display available options (--help-hidden for more).
For coverage output of files included from the main source file,
add the main file name followed by ## as a prefix to the output
file names. This can be combined with the --preserve-paths op-
tion to use complete paths for both the main file and the in-
Do not output any .gcov files. Summary information is still dis-
-o=<DIR|FILE>, --object-directory=<DIR>, --object-file=<FILE>
Find objects in DIR or based on FILE's path. If you specify a
particular object file, the coverage data files are expected to
have the same base name with .gcno and .gcda extensions. If you
specify a directory, the files are expected in that directory
with the same base name as the source file.
Preserve path components when naming the coverage output files.
In addition to the source file name, include the directories
from the path to that file. The directories are separate by #
characters, with . directories removed and .. directories re-
placed by ^ characters. When used with the --long-file-names op-
tion, this applies to both the main file name and the included
Include unconditional branches in the output for the
Display the version of llvm-cov.
llvm-cov returns 1 if it cannot read input files. Otherwise, it exits
Maintained by The LLVM Team (http://llvm.org/).
2003-2016, LLVM Project
3.5 2016-10-07 LLVM-COV(1)