Ubuntu Manpage: llvm-cov - emit coverage information

Provided by: llvm-20_20.1.2-0ubuntu1_amd64

NAME

       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.

COMMANDS

       • gcov

       • show

       • report

       • export

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-line-counts
Show the execution counts for each line. Defaults to true, unless another -show option is used.

-show-expansions
Expand inclusions, such as preprocessor macros or textual inclusions, inline in the display of the
source file. Defaults to false.

-show-instantiations
For source regions that are instantiated multiple times, such as templates in C++, show each
instantiation separately as well as the combined summary. Defaults to true.

-show-regions
Show the execution counts for each region by displaying a caret that points to the character where
the region starts. Defaults to false.

-show-line-counts-or-regions
Show the execution counts for each line if there is only one region on the line, but show the
individual regions if there are multiple on the line. Defaults to false.

-show-directory-coverage
Generate an index file in each directory that contains at least one source file with a top level
index showing aggregates. Defaults to false.

-use-color
Enable or disable color output. By default this is autodetected.

-arch=[*NAMES*]
Specify a list of architectures such that the Nth entry in the list corresponds to the Nth
specified binary. If the covered object is a universal binary, this specifies the architecture to
use. It is an error to specify an architecture that is not included in the universal binary or to
use an architecture that does not match a non-universal binary.

-name=<NAME>
Show code coverage only for functions with the given name.

-name-allowlist=<FILE>
Show code coverage only for functions listed in the given file. Each line in the file should start
with allowlist_fun:, immediately followed by the name of the function to accept. This name can be
a wildcard expression.

-name-regex=<PATTERN>
Show code coverage only for functions that match the given regular expression.

-ignore-filename-regex=<PATTERN>
Skip source code files with file paths that match the given regular expression.

-format=<FORMAT>
Use the specified output format. The supported formats are: “text”, “html”.

-tab-size=<TABSIZE>
Replace tabs with <TABSIZE> spaces when preparing reports. Currently, this is only supported for
the html format.

-output-dir=PATH
Specify a directory to write coverage reports into. If the directory does not exist, it is
created. When used in function view mode (i.e when -name or -name-regex are used to select
specific functions), the report is written to PATH/functions.EXTENSION. When used in file view
mode, a report for each file is written to PATH/REL_PATH_TO_FILE.EXTENSION.

-Xdemangler=<TOOL>|<TOOL-OPTION>
Specify a symbol demangler. This can be used to make reports more human-readable. This option can
be specified multiple times to supply arguments to the demangler (e.g -Xdemangler c++filt
-Xdemangler -n for C++). The demangler is expected to read a newline-separated list of symbols
from stdin and write a newline-separated list of the same length to stdout.

-num-threads=N, -j=N
Use N threads to write file reports (only applicable when -output-dir is specified). When N=0,
llvm-cov auto-detects an appropriate number of threads to use. This is the default.

-compilation-dir=<dir>
Directory used as a base for relative coverage mapping paths. Only applicable when binaries have
been compiled with one of -fcoverage-prefix-map -fcoverage-compilation-dir, or
-ffile-compilation-dir.

-line-coverage-gt=<N>
Show code coverage only for functions with line coverage greater than the given threshold.

-line-coverage-lt=<N>
Show code coverage only for functions with line coverage less than the given threshold.

-region-coverage-gt=<N>
Show code coverage only for functions with region coverage greater than the given threshold.

-region-coverage-lt=<N>
Show code coverage only for functions with region coverage less than the given threshold.

-path-equivalence=<from>,<to>
Map the paths in the coverage data to local source file paths. This allows you to generate the
coverage data on one machine, and then use llvm-cov on a different machine where you have the same
files on a different path. Multiple -path-equivalence arguments can be passed to specify different
mappings. Each argument consists of a source path <from> and its corresponding local path <to>.
The mappings are applied in the order they are specified. If multiple mappings can be applied to a
single path, the first mapping encountered is used.

-coverage-watermark=<high>,<low>
Set high and low watermarks for coverage in html format output. This allows you to set the high
and low watermark of coverage as desired, green when coverage >= high, red when coverage < low,
and yellow otherwise. Both high and low should be between 0-100 and high > low.

-debuginfod
Use debuginfod to look up coverage mapping for binary IDs present in the profile but not in any
object given on the command line. Defaults to true if debuginfod is compiled in and configured via
the DEBUGINFOD_URLS environment variable.

-debug-file-directory=<dir>
Provides local directories to search for objects corresponding to binary IDs in the profile (as
with debuginfod). Defaults to system build ID directories.

-check-binary-ids
Fail if an object file cannot be found for a binary ID present in the profile, neither on the
command line nor via binary ID lookup.

REPORT COMMAND

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

DESCRIPTION
The llvm-cov report command displays a summary of the 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).

If no source files are provided, a summary line is printed for each file in the coverage data. If any
files are provided, summaries can be shown for each function in the listed files if the -show-functions
option is enabled.

For information on compiling programs for coverage and generating profile data, see SHOW COMMAND.

OPTIONS
-use-color[=VALUE]
Enable or disable color output. By default this is autodetected.

-arch=<name>
If the covered binary is a universal binary, select the architecture to use. It is an error to
specify an architecture that is not included in the universal binary or to use an architecture
that does not match a non-universal binary.

-show-region-summary
Show statistics for all regions. Defaults to true.

-show-branch-summary
Show statistics for all branch conditions. Defaults to true.

-show-mcdc-summary
Show MC/DC statistics. Defaults to false.

-show-functions
Show coverage summaries for each function. Defaults to false.

-show-instantiation-summary
Show statistics for all function instantiations. Defaults to false.

-ignore-filename-regex=<PATTERN>
Skip source code files with file paths that match the given regular expression.

-debuginfod
Attempt to look up coverage mapping from objects using debuginfod. This is attempted by default
for binary IDs present in the profile but not provided on the command line, so long as debuginfod
is compiled in and configured via DEBUGINFOD_URLS.

-debug-file-directory=<dir>
Provides a directory to search for objects corresponding to binary IDs in the profile.

-check-binary-ids
Fail if an object file cannot be found for a binary ID present in the profile, neither on the
command line nor via binary ID lookup.

EXPORT COMMAND

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

DESCRIPTION
The llvm-cov export command exports coverage data of the binaries BIN… using the profile data PROFILE in
either JSON or lcov trace file format.

When exporting JSON, the regions, functions, branches, expansions, and summaries of the coverage data
will be exported. When exporting an lcov trace file, the line-based coverage, branch coverage, and
summaries will be exported.

The exported data can optionally be filtered to only export the coverage for the files listed in SOURCE….

For information on compiling programs for coverage and generating profile data, see SHOW COMMAND.

OPTIONS
-arch=<name>
If the covered binary is a universal binary, select the architecture to use. It is an error to
specify an architecture that is not included in the universal binary or to use an architecture
that does not match a non-universal binary.

-format=<FORMAT>
Use the specified output format. The supported formats are: “text” (JSON), “lcov”.

-summary-only
Export only summary information for each file in the coverage data. This mode will not export
coverage information for smaller units such as individual functions or regions. The result will
contain the same information as produced by the llvm-cov report command, but presented in JSON or
lcov format rather than text.

-ignore-filename-regex=<PATTERN>
Skip source code files with file paths that match the given regular expression.

-skip-expansions
Skip exporting macro expansion coverage data.

-skip-functions
Skip exporting per-function coverage data.

-num-threads=N, -j=N
Use N threads to export coverage data. When N=0, llvm-cov auto-detects an appropriate number of
threads to use. This is the default.

-debug-file-directory=<dir>
Provides a directory to search for objects corresponding to binary IDs in the profile.

-check-binary-ids
Fail if an object file cannot be found for a binary ID present in the profile, neither on the
command line nor via binary ID lookup.

CONVERT-FOR-TESTING COMMAND

       WARNING:
          This command is for the LLVM developers who are working on llvm-cov only.

   SYNOPSIS
       llvm-cov convert-for-testing BIN -o OUT

   DESCRIPTION
       The  llvm-cov  convert-for-testing  command serves the purpose of testing llvm-cov itself. It can extract
       all code coverage data from the binary BIN to the file OUT, thereby reducing the size of test files.  The
       output file typically bears the .covmapping extension.

       The .covmapping files can be read back by llvm-cov just as ordinary binary files.

AUTHOR

       Maintained by the LLVM Team (https://llvm.org/).

COPYRIGHT

       2003-2025, LLVM Project

15                                                 2025-04-03                                        LLVM-COV(1)