llvm-cov - emit coverage information#

SYNOPSIS#

llvm-cov command [args…]

DESCRIPTION#

The llvm-cov tool shows code coverage information for programs that are instrumented to emit profile data. It can be used to work with gcov-style coverage or with clang’s instrumentation based profiling.

If the program is invoked with a base name of gcov, it will behave as if the llvm-cov gcov command were called. Otherwise, a command should be provided.

GCOV COMMAND#

SYNOPSIS#

llvm-cov gcov [options] SOURCEFILE

DESCRIPTION#

The llvm-cov gcov tool reads code coverage data files and displays the coverage 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 gcov, 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.)

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 separate .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 included.

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 accessible, but you will then need to copy the .gcda files back to the object file directories where llvm-cov gcov expects to find them.

Once you have generated the coverage data files, run llvm-cov gcov 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 compiler. The results for the specified source file are written to a file named by appending a .gcov suffix. A separate output file is also created for each file included by the main source file, also with a .gcov suffix added.

The basic content of an .gcov 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 executable code. If a line contains code but that code was never executed, the count is displayed as #####.

OPTIONS#

-a, --all-blocks#: 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 entire line.

-b, --branch-probabilities#: Display conditional branch probabilities and a summary of branch information.

-c, --branch-counts#: Display branch counts instead of probabilities (requires -b).

-m, --demangled-names#: Demangle function names.

-f, --function-summaries#: 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).

-l, --long-file-names#: 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 option to use complete paths for both the main file and the included file.

-n, --no-output#: Do not output any .gcov files. Summary information is still displayed.

-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.

-p, --preserve-paths#: 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 replaced by ^ characters. When used with the –long-file-names option, this applies to both the main file name and the included file name.

-r#: Only dump files with relative paths or absolute paths with the prefix specified by -s.

-s <string>#: Source prefix to elide.

-t, --stdout#: Print to stdout instead of producing .gcov files.

-u, --unconditional-branches#: Include unconditional branches in the output for the –branch-probabilities option.

-version#: Display the version of llvm-cov.

-x, --hash-filenames#: Use md5 hash of file name when naming the coverage output files. The source file name will be suffixed by ## followed by MD5 hash calculated for it.

EXIT STATUS#

llvm-cov gcov returns 1 if it cannot read input files. Otherwise, it exits with zero.

SHOW COMMAND#

SYNOPSIS#

llvm-cov show [options] -instr-profile PROFILE [BIN] [-object BIN]… [-sources] [SOURCE]…

DESCRIPTION#

The llvm-cov show command shows line by line coverage of the binaries BIN… using the profile data PROFILE. It can optionally be filtered to only show the coverage for the files listed in SOURCE….

BIN may be an executable, object file, dynamic library, or archive (thin or otherwise).

To use llvm-cov show, you need a program that is compiled with instrumentation to emit profile and coverage data. To build such a program with clang use the -fprofile-instr-generate and -fcoverage-mapping flags. If linking with the clang driver, pass -fprofile-instr-generate to the link stage to make sure the necessary runtime libraries are linked in.

The coverage information is stored in the built executable or library itself, and this is what you should pass to llvm-cov show as a BIN argument. The profile data is generated by running this instrumented program normally. When the program exits it will write out a raw profile file, typically called default.profraw, which can be converted to a format that is suitable for the PROFILE argument using the llvm-profdata merge tool.

OPTIONS#

-show-branches=<VIEW>#: Show coverage for branch conditions in terms of either count or percentage. The supported views are: “count”, “percent”.

-show-mcdc#: Show modified condition/decision coverage (MC/DC) for each applicable boolean expression.

-show-mcdc-non-executed-vectors#: When showing MC/DC details, also list test vectors that were not executed (for example in a Not executed section after the executed vectors). By default, only executed test vectors are shown.