geninfo(1)

NAME
geninfo - Generate tracefiles from GCOV coverage data files

SYNOPSIS
geninfo [-h|--help] [--version] [-q|--quiet] [-v|--verbose] [--debug]
    [--comment comment-string]
    [-i|--initial] [--all]
    [-t|--test-name test-name]
    [-o|--output-filename filename] [-f|--follow]
    [-b|--base-directory directory]
    [--build-directory directory]
    [--branch-coverage]
    [--mcdc-coverage]
    [--checksum] [--no-checksum]
    [--compat-libtool] [--no-compat-libtool]
    [--gcov-tool tool]
    [--parallel|-j [integer]]
    regexp]
    [--memory integer_num_Mb]
    [--msg-log [log_file_name]]
    [--ignore-errors errors]
    [--expect-message-count message_type=expr[,message_type=expr..]]
    [--keep-going]
    [--preserve]
    [--filter type]
    [--demangle-cpp[param]]
    [--no-recursion] [--external] [--no-external]
    [--sort-input]
    [--config-file config-file] [--no-markers]
    [--profile [profile-file]]
    [--derive-func-data] [--compat mode=on|off|auto]
    [--rc keyword=value]
    [--include glob_pattern]
    [--exclude glob_pattern]
    [--erase-functions regexp_pattern]
    [--substitute regexp_pattern]
    [--omit-lines regexp_pattern]
    [--fail-under-branches percentage]
    [--fail-under-lines percentage]
    [--forget-test-names]
    [--context-script script_file]
    [--criteria-script script_file]
    [--resolve-script script_file]
    [--version-script script_file]
    [--tempdir dirname]
    directory

DESCRIPTION
Use geninfo to create LCOV tracefiles from GCC and LLVM/Clang coverage data files (see --gcov-tool for considerations when working with LLVM). You can use genhtml to create an HTML report from a tracefile.
Note that geninfo is called by lcov --capture, so there is typically no need to call it directly.
Unless the --output-filename option is specified geninfo writes its output to one file with .info filename extension per input file.
Note also that the current user needs write access to both directory as well as to the original source code location. This is necessary because some temporary files have to be created there during the conversion process.
By default, geninfo collects line and function coverage data. Neither branch nor MC/DC data is not collected by default; you can use the --branch-coverage and --mcdc-coverage command line options to enable them, or you can permanently enable them by adding branch_coverage = 1 and/or mcdc_coverage = 1 to your personal, group, or site lcov configuration file. See man lcovrc(5) for details.

  File types
A tracefile is a coverage data file in the format used by all LCOV tools such as geninfo, lcov, and genhtml. By convention, tracefiles have a .info filename extension. See "Tracefile format" below for a description of the file format.
A .gcda file is a compiler-specific file containing run-time coverage data. It is created and updated when a program compiled with GCC/LLVM's --coverage option is run to completion. geninfo reads .gcda files in its default mode of operation. Note: earlier compiler versions used the .da filename extension for this file type.
A .gcno file is a compiler-specific file containing static, compile-time coverage data. It is created when source code is compiled with GCC/LLVM's --coverage option. geninfo reads .gcno files when option --initial is specified. Note: earlier compiler versions used .bb and .bbg filename extensions for this file type.
A .gcov file is a textual or JSON representation of the data found in .gcda and .gcno files. It is created by the gcov tools that is part of GCC (see --gcov-tool for LLVM considerations). There are multiple gcov file format versions, including textual, intermediate, and JSON format. geninfo internally uses gcov to extract coverage data from .gcda and .gcno files using the best supported gcov file format.
See the gcov man page for more information on .gcda, .gcno and .gcov output formats.

  Exclusion markers
To exclude specific lines of code from a tracefile, you can add exclusion markers to the source code. Additionally you can exclude specific branches from branch coverage without excluding the involved lines from line and function coverage. Exclusion markers are keywords which can for example be added in the form of a comment. See man lcovrc(5) how to override some of them. The following markers are recognized by geninfo: LCOV_EXCL_LINE
    Lines containing this marker will be excluded.
LCOV_EXCL_START
    Marks the beginning of an excluded section. The current line is part of this section.
LCOV_EXCL_STOP
    Marks the end of an excluded section. The current line not part of this section.
LCOV_EXCL_BR_LINE
    Lines containing this marker will be excluded from branch coverage.
LCOV_EXCL_BR_START
    Marks the beginning of a section which is excluded from branch coverage. The current line is part of this section.
LCOV_EXCL_BR_STOP
    Marks the end of a section which is excluded from branch coverage. The current line not part of this section.
LCOV_EXCL_EXCEPTION_BR_LINE
    Lines containing this marker will be excluded from exception branch coverage: Exception branches will be ignored, but non-exception branches will not be affected.
LCOV_EXCL_EXCEPTION_BR_START
    Marks the beginning of a section which is excluded from exception branch coverage. The current line is part of this section.
LCOV_EXCL_EXCEPTION_BR_STOP
    Marks the end of a section which is excluded from exception branch coverage. The current line not part of this section

OPTIONS
In general, (almost) all geninfo options can also be specified in your personal, group, project, or site configuration file - see man lcovrc(5) for details. -b directory
--base-directory directory
    Use directory as base directory for relative paths. Use this option to specify the base directory of a build-environment when geninfo produces error messages like:
        ERROR: could not read source file /home/user/project/subdir1/subdir2/subdir1/subdir2/file.c
    In this example, use /home/user/project as base directory. This option is required when using geninfo on projects built with libtool or similar build environments that work with a base directory, i.e. environments, where the current working directory when invoking the compiler is not the same directory in which the source code file is located. Note that this option will not work in environments where multiple base directories are used. In that case use configuration file setting geninfo_auto_base=1 (see man lcovrc(5)).
--build-directory build_dir
    Search for .gcno data files from build_dir rather finding them only adjacent to the corresponding .o and/or .gcda file. By default, geninfo expects to find the .gcno and .gcda files (compile- and run-time data, respectively) in the same directory.
    When this option is used:
        geninfo path1 --build-directory path2 ...
    then geninfo will look for .gcno file
        path2/relative/path/to/da_base.gcno
    when it finds .gcda file
        path1/relative/path/to/da_base.gcda.
    Use this option when you have used the GCOV_PREFIX environment variable to direct the gcc or llvm runtime environment to write coverage data files to somewhere other than the directory where the code was originally compiled. See gcc(1) and/or search for GCOV_PREFIX and GCOV_PREFIX_STRIP. This option can be used several times to specify multiple alternate directories to look for .gcno files. This may be useful if your application uses code which is compiled in many separate locations - for example, common libraries that are shared between teams.
--source-directory dirname
    Add 'dirname' to the list of places to look for source files.
    For relative source file paths found in the gcov data - possibly after substitutions have been applied, geninfo will first look for the path from 'cwd' (where genhtml was invoked) and then from each alternate directory name in the order specified. The first location matching location is used. This option can be specified multiple times, to add more directories to the source search path.
--branch-coverage
    Collect retain branch coverage data. This is equivalent to using the option "--rc branch_coverage=1"; the option was added to better match the genhml interface.
--mcdc-coverage
    Collect retain MC/DC data. This is equivalent to using the option "--rc mcdc_coverage=1". MC/DC coverage capture is supported for GCC versions 14.2 and higher, or LLVM versions 18.1 and higher.
    See llvm2lcov --help for details on MC/DC data capture in LLVM.
    See the MC/DC section of man genhtml(1) for more details
--checksum
--no-checksum
    Specify whether to generate checksum data when writing tracefiles. Use --checksum to enable checksum generation or --no-checksum to disable it. Checksum generation is disabled by default. When checksum generation is enabled, a checksum will be generated for each source code line and stored along with the coverage data. This checksum will be used to prevent attempts to combine coverage data from different source code versions. If you don't work with different source code versions, disable this option to speed up coverage data processing and to reduce the size of tracefiles. Note that this options is somewhat subsumed by the --version-script option - which does something similar, but at the 'whole file' level.
--compat mode=value[,mode=value,...]
    Set compatibility mode. Use --compat to specify that geninfo should enable one or more compatibility modes when capturing coverage data. You can provide a comma-separated list of mode=value pairs to specify the values for multiple modes. Valid values are: on
        Enable compatibility mode.
    off
        Disable compatibility mode.
    auto
        Apply auto-detection to determine if compatibility mode is required. Note that auto-detection is not available for all compatibility modes.
    If no value is specified, 'on' is assumed as default value. Valid modes are: libtool
        Enable this mode if you are capturing coverage data for a project that was built using the libtool mechanism. See also --compat-libtool. The default value for this setting is 'on'.
    hammer
        Enable this mode if you are capturing coverage data for a project that was built using a version of GCC 3.3 that contains a modification (hammer patch) of later GCC versions. You can identify a modified GCC 3.3 by checking the build directory of your project for files ending in the extension .bbg. Unmodified versions of GCC 3.3 name these files .bb. The default value for this setting is 'auto'.
    split_crc
        Enable this mode if you are capturing coverage data for a project that was built using a version of GCC 4.6 that contains a modification (split function checksums) of later GCC versions. Typical error messages when running geninfo on coverage data produced by such GCC versions are 'out of memory' and 'reached unexpected end of file'. The default value for this setting is 'auto'
--compat-libtool
--no-compat-libtool
    Specify whether to enable libtool compatibility mode. Use --compat-libtool to enable libtool compatibility mode or --no-compat-libtool to disable it. The libtool compatibility mode is enabled by default. When libtool compatibility mode is enabled, geninfo will assume that the source code relating to a .gcda file located in a directory named ".libs" can be found in its parent directory. If you have directories named ".libs" in your build environment but don't use libtool, disable this option to prevent problems when capturing coverage data.
--config-file config-file
    Specify a configuration file to use. See man lcovrc(5) for details of the file format and options. Also see the config_file entry in the same man page for details on how to include one config file into another. When this option is specified, neither the system-wide configuration file /etc/lcovrc, nor the per-user configuration file ~/.lcovrc is read. This option may be useful when there is a need to run several instances of geninfo with different configuration file options in parallel. Note that this option must be specified in full - abbreviations are not supported.
--profile [ profile-data-file ]
    Tell the tool to keep track of performance and other configuration data. If the optional profile-data-file is not specified, then the profile data is written to a file named with the same basename as the --output-filename, with suffix .json appended.
--derive-func-data
    Calculate function coverage data from line coverage data. Use this option to collect function coverage data, even if the version of the gcov tool installed on the test system does not provide this data. lcov will instead derive function coverage data from line coverage data and information about which lines belong to a function.
--external
--no-external
    Specify whether to capture coverage data for external source files. External source files are files which are not located in one of the directories specified by --directory or --base-directory. Use --external to include coverpoints in external source files while capturing coverage data or --no-external to exclude them. If your --directory or --base-directory path contains a soft link, then actual target directory is not considered to be "internal" unless the --follow option is used. The --no-external option is somewhat of a blunt instrument; the --exclude and --include options provide finer grained control over which coverage data is and is not included if your project structure is complex and/or --no-external does not do what you want. Data for external source files is included by default.
-f
--follow
    Follow links when searching .gcda files, as well as to decide whether a particular (symbolically linked) source directory is "internal" to the project or not - see the --no-external option, above, for more information. The --follow command line option is equivalent to the geninfo_follow_symlinks config file option. See man lcovrc(5) for more information.
--sort-input
    Specify whether to sort file names before capture and/or aggregation. Sorting reduces certain types of processing order-dependent output differences. See the sort_input section in man lcovrc(5).
--gcov-tool tool
    Specify the location of the gcov tool. If the --gcov-tool option is used multiple times, then the arguments are concatenated when the callback is executed - similar to how the gcc -Xlinker parameter works. This provides a possibly easier way to pass arguments to your tool, without requiring a wrapper script. In that case, your callback will be executed as: tool-0 'tool-1; ... 'filename'. Note that the second and subsequent arguments are quoted when passed to the shell, in order to handle parameters which contain spaces. The --gcov-tool argument may be a split_char separated string - see man(4) lcovrc. A common use for this option is to enable LLVM:
        geninfo --gcov-tool llvm-cov --gcov-tool gcov ...
        geninfo --gcov-tool llvm-cov,gcov ...
    Note: 'llvm-cov gcov da_file_name' will generate output in gcov-compatible format as required by lcov. If not specified, 'gcov' is used by default.
-h
--help
    Print a short help text, then exit.
--include pattern
    Include source files matching pattern. Use this switch if you want to include coverage data for only a particular set of source files matching any of the given patterns. Multiple patterns can be specified by using multiple --include command line switches. The patterns will be interpreted as shell wildcard patterns (note that they may need to be escaped accordingly to prevent the shell from expanding them first). See the lcov man page for details
--exclude pattern
    Exclude source files matching pattern. Use this switch if you want to exclude coverage data from a particular set of source files matching any of the given patterns. Multiple patterns can be specified by using multiple --exclude command line switches. The patterns will be interpreted as shell wildcard patterns (note that they may need to be escaped accordingly to prevent the shell from expanding them first). Note: The pattern must be specified to match the absolute path of each source file. Can be combined with the --include command line switch. If a given file matches both the include pattern and the exclude pattern, the exclude pattern will take precedence. See the lcov man page for details.
--erase-functions regexp
    Exclude coverage data from lines which fall within a function whose name matches the supplied regexp. Note that this is a mangled or demangled name, depending on whether the --demangle-cpp option is used or not. Note that this option requires that you use a gcc version which is new enough to support function begin/end line reports or that you configure the tool to derive the required dta - see the derive_function_end_line discussion in the lcovrc man page.
--substitute regexp_pattern
    Apply Perl regexp regexp_pattern to source file names found during processing. This is useful when the path name reported by gcov does not match your source layout and the file is not found. See the lcov man page for more details.
--omit-lines regexp
    Exclude coverage data from lines whose content matches regexp. Use this switch if you want to exclude line, branch, and MC/DC coverage data for some particular constructs in your code (e.g., some complicated macro). See the lcov man page for details.
--forget-test-names
    If non-zero, ignore testcase names in tracefile - i.e., treat all coverage data as if it came from the same testcase. This may improve performance and reduce memory consumption if user does not need per-testcase coverage summary in coverage reports. This option can also be configured permanently using the configuration file option forget_testcase_names.
--msg-log [ log_file_name ]
    Specify location to store error and warning messages (in addition to writing to STDERR). If log_file_name is not specified, then default location is used.
--ignore-errors errors
    Specify a list of errors after which to continue processing. Use this option to specify a list of one or more classes of errors after which geninfo should continue processing instead of aborting. Note that the tool will generate a warning (rather than a fatal error) unless you ignore the error two (or more) times:
        geninfo ... --ignore-errors unused,unused
    errors can be a comma-separated list of the following keywords:

    branch:
        branch ID (2nd field in the .info file 'BRDA' entry) does not follow expected integer sequence.

    callback:
        Version script error.

    child:
        child process returned non-zero exit code during --parallel execution. This typically indicates that the child encountered an error: see the log file immediately above this message. In contrast: the parallel error indicates an unexpected/unhandled exception in the child process - not a 'typical' lcov error.

    corrupt:
        corrupt/unreadable file found.

    count:
        An excessive number of messages of some class have been reported - subsequent messages of that type will be suppressed. The limit can be controlled by the 'max_message_count' variable. See the lcovrc man page.

    deprecated:
        You are using a deprecated option. This option will be removed in an upcoming release - so you should change your scripts now.

    empty:
        the .info data file is empty (e.g., because all the code was 'removed' or excluded.

    excessive:
        your coverage data contains a suspiciously large 'hit' count which is unlikely to be correct - possibly indicating a bug in your toolchain. See the excessive_count_threshold section in man lcovrc(5) for details.

    fork:
        Unable to create child process during --parallel execution.
        If the message is ignored ( --ignore-errors fork ), then genhtml will wait a brief period and then retry the failed execution.
        If you see continued errors, either turn off or reduce parallelism, set a memory limit, or find a larger server to run the task.

    format:
        Unexpected syntax or value found in .info file - for example, negative number or zero line number encountered.

    gcov:
        the gcov tool returned with a non-zero return code.

    graph:
        the graph file could not be found or is corrupted.

    inconsistent:
        your coverage data is internally inconsistent: it makes two or more mutually exclusive claims. For example, some expression is marked as both an exception branch and not an exception branch. (See man genhtml(1) for more details.

    internal:
        internal tool issue detected. Please report this bug along with a testcase.

    mismatch:
        Incorrect information found in coverage data and/or source code - for example, the source code contains overlapping exclusion directives.

    missing:
        File does not exist or is not readable.

    negative:
        negative 'hit' count found. Note that negative counts may be caused by a known GCC bug - see
          https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68080 and try compiling with "-fprofile-update=atomic". You will need to recompile, re-run your tests, and re-capture coverage data.

    package:
        a required perl package is not installed on your system. In some cases, it is possible to ignore this message and continue - however, certain features will be disabled in that case.

    parallel:
        various types of errors related to parallelism - i.e., a child process died due to an error. The corresponding error message appears in the log file immediately before the parallel error. If you see an error related to parallel execution that seems invalid, it may be a good idea to remove the --parallel flag and try again. If removing the flag leads to a different result, please report the issue (along with a testcase) so that the tool can be fixed.

    parent:
        the parent process exited while child was active during --parallel execution. This happens when the parent has encountered a fatal error - e.g. an error in some other child which was not ignored. This child cannot continue working without its parent - and so will exit.

    path:
        some file paths were not resolved - e.g., .gcno file corresponding to some .gcda was not found see --build-directory option for additional information.

    range:
        Coverage data refers to a line number which is larger than the number of lines in the source file. This can be caused by a version mismatch or by an issue in the gcov data.

    source:
        the source code file for a data set could not be found.

    `<

    unsupported:
        the requested feature is not supported for this tool configuration. For example, function begin/end line range exclusions use some GCOV features that are not available in older GCC releases.

    unused:
        the include/exclude/erase/omit/substitute pattern did not match any file pathnames.

    usage:
        unsupported usage detected - e.g. an unsupported option combination.

    utility:
        a tool called during processing returned an error code (e.g., 'find' encountered an unreadable directory).

    version:
        revision control IDs of the file which we are trying to merge are not the same - line numbering and other information may be incorrect.

    Also see the --ignore-errors section in man genhtml(1). The description there may be more complete and/or more fully explained. See man lcovrc(5)
     for a discussion of the 'max_message_count' parameter which can be used to control the number of warnings which are emitted before all subsequent messages are suppressed. This can be used to reduce log file volume.
--expect-message-count message_type:expr[,message_type:expr]
    Give geninfo a constraint on the number of messages of one or more types which are expected to be produced during execution. If the constraint is not true, then generate an error of type count (see above). See man genhtml(1) for more details about the flag, as well as the expect_message_count section in man lcovrc(5) for a description of the equivalent configuration file option.
--keep-going
    Do not stop if error occurs: attempt to generate a result, however flawed. This command line option corresponds to the stop_on_error [0|1] lcovrc option. See man lcovrc(5) for more details.
--fail-under-lines percentage
    Use this option to tell geninfo to exit with a status of 1 if the total line coverage is less than percentage. See man lcov(1) for more details.
--preserve
    Preserve intermediate data files (e.g., for debugging). By default, intermediate files are deleted.
--filter filters
    Specify a list of coverpoint filters to apply to input data. See the genhtml man page for details.
--demangle-cpp [param]
    Demangle C++ method and function names in captured output. See the genhtml man page for details.
-i
--initial
    Capture initial zero coverage data. Run geninfo with this option on the directories containing .bb, .bbg or .gcno files before running any test case. The result is a "baseline" coverage data file that contains zero coverage for every instrumented line and function. Combine this data file (using lcov -a) with coverage data files captured after a test run to ensure that the percentage of total lines covered is correct even when not all object code files were loaded during the test. Also see the --all flag, below. Note: the --initial option is not supported for gcc versions less than 6, and does not generate branch coverage information for gcc versions less than 8.
--all
    Capture coverage data from both compile time (.gcno) data files which do not have corresponding runtime (.gcda) data files, as well as from those that do have corresponding runtime data. There will be no runtime data unless some executable which links the corresponding object file has run to completion. Note that the execution count of coverpoints found only in files which do not have any runtime data will be zero. This flag is ignored if the --initial flag is set. Using the --all flag is equivalent to executing both geninfo --initial ... and geninfo ... and merging the result. Also see the geninfo_capture_all entry in man(5) lcovrc.
--no-markers
    Unless the --no-markers option is used, geninfo will apply both region and branch_region filters to the captured coverae data. Use this option if you want to get coverage data without regard to exclusion markers in the source code file. If any --filter options are applied, then the default region filters are not used. --no-markers should not be specified along with --filter.
--no-recursion
    Use this option if you want to get coverage data for the specified directory only without processing subdirectories.
-o output-filename
--output-filename output-filename
    Write all data to output-filename. If you want to have all data written to a single file (for easier handling), use this option to specify the respective filename. By default, one tracefile will be created for each processed .gcda file.
--context-script script
    Use script to collect additional tool execution context information - to aid in infrastructure debugging and/or tracking. See the genhtml man page for more details on the context script.
--criteria-script script
    Use script to test for coverage acceptance criteria. See the genhtml man page for more details on the criteria script. Note that geninfo does not keep track of date and owner information (see the --annotate-script entry in the genhtml man page) - so this information is not passed to the geninfo callback.
--resolve-script script
    Use script to find the file path for some source or GCNO file which appears in an input data file if the file is not found after applying --substitute patterns and searching the --source-directory or --build-directory list. This option is equivalent to the resolve_script config file option.
    In addition, the geninfo_follow_path_links config file option can be used to resolve source paths to their actual target. See man lcovrc(5) for details.
--version-script script
    Use script to get a source file's version ID from revision control when extracting data. The ID is used for error checking when merging .info files.
    See the genhtml man page for more details on the version script. -v
    --verbose
        Increment informational message verbosity. This is mainly used for script and/or flow debugging - e.g., to figure out which data file are found, where. Also see the --quiet flag. Messages are sent to stdout unless there is no output file (i.e., if the coverage data is written to stdout rather than to a file) and to stderr otherwise.
    -q
    --quiet
        Decrement informational message verbosity. Decreased verbosity will suppress 'progress' messages for example - while error and warning messages will continue to be printed.
    --debug
        Increment 'debug messages' verbosity. This is useful primarily to developers who want to enhance the lcov tool suite.
    --comment comment_string
        Append comment_string to list of comments emitted into output result file. This option may be specified multiple times. Comments are printed at the top of the file, in the order they were specified. Comments can be useful to document the conditions under which the trace file was generated: host, date, environment, etc.
    --parallel [ integer ]
    -j [ integer ]
        Specify parallelism to use during processing (maximum number of forked child processes). If the optional integer parallelism parameter is zero or is missing, then use to use up the number of cores on the machine. Default is to use a single process (no parallelism). The - option described below may be necessary to enable parallelism to succeed in the presence of data files which consume excessive memory in gcov. Also see the memory, memory_percentage, max_fork_fails, fork_fail_timeout, geninfo_chunk_size and geninfo_interval_update entries in man lcovrc(5) for a description of some options which may aid in parameter tuning and performance optimization.
    --large-file regexp
        GCDA files whose name matches a --large-file regexp are processed serially - not in parallel with other files - so that their gcov process can use all available system memory.
        Use this option is you see errors related to memory allocation from gcov.
        This feature is exactly as if you had moved the matching GCDA files to another location and processed them serially, then processed remaining GDCA files in parallel and merged the results. This option may be used multiple times to specify more than one regexp.
    --memory integer
        Specify the maximum amount of memory to use during parallel processing, in Mb. Effectively, the process will not fork() if this limit would be exceeded. Default is 0 (zero) - which means that there is no limit. This option may be useful if the compute farm environment imposes strict limits on resource utilization such that the job will be killed if it tries to use too many parallel children - but the user does now know a priori what the permissible maximum is. This option enables the tool to use maximum parallelism - up to the limit imposed by the memory restriction. The configuration file memory_percentage option provided another way to set the maximum memory consumption. See man lcovrc(5) for details.
    --rc keyword=value
        Override a configuration directive. Use this option to specify a keyword=value statement which overrides the corresponding configuration statement in the lcovrc configuration file. You can specify this option more than once to override multiple configuration statements. See man lcovrc(5) for a list of available keywords and their meaning.
    -t testname
    --test-name testname
        Use test case name testname for resulting data. Valid test case names can consist of letters, decimal digits and the underscore character ('_'). This proves useful when data from several test cases is merged (i.e. by simply concatenating the respective tracefiles) in which case a test name can be used to differentiate between data from each test case.
    --version
        Print version number, then exit.
    --tempdir dirname
        Write temporary and intermediate data to indicated directory. Default is "/tmp".

TRACEFILE FORMAT
Following is a quick description of the tracefile format as used by genhtml, geninfo and lcov. A tracefile is made up of several human-readable lines of text, divided into sections. If the ---comment comment_string option is supplied, then
     #comment_string
will appear at the top of the tracefile. There is no space before or after the # character. If available, a tracefile begins with the testname which is stored in the following format:
    TN:<test name>
For each source file referenced in the .gcda file, there is a section containing filename and coverage data:
    SF:<path to the source file>
An optional source code version ID follows:
    VER:<version ID>
If present, the version ID is compared before file entries are merged (see lcov --add-tracefile ), and before the 'source detail' view is generated by genhtml. See the --version-script callback_script documentation and the sample usage in the lcov regression test examples. Function coverage data follows. Note that the format of the function coverage data has changed from LCOV 2.2 onward. The tool continues to be able to read the old format but now writes only the new format. This change was made so that function filter outcome is persistent in the generated tracefile. Functions and their aliases are recorded contiguously: First, the leader:
    FNL:<index>,<line number of function start>[,line number of function end>]
Then the aliases of the function; there will be at least one alias. All aliases of a particular function share the same index.
    FNA:<index>,<execution count>,<name>
The now-obsolete function data format is:
        FN:<line number of function start>,[<line number of function end>,]<function name>
    The 'end' line number is optional, and is generated only if the compiler/toolchain version is recent enough to generate the data (e.g., gcc 9 or newer). This data is used to support the --erase-functions and --show-proportions options. If the function end line data is not available, then these features will not work. Next, there is a list of execution counts for each instrumented function:
        FNDA:<execution count>,<function name>
This list is followed by two lines containing the number of functions found and hit:
    FNF:<number of functions found>
    FNH:<number of function hit>
Note that, as of LCOV 2.2, these numbers count function groups - not the individual aliases. Branch coverage information is stored one line per branch:
    BRDA:<line_number>,[<exception>]<block>,<branch>,<taken>
<line_number> is the line number where the branch is found - and is expected to be a non-zero integer.
<block> and <branch> serve to uniquely define a particular edge in the expression tree of a particular conditional found on the associated line.
Within a particular line, <block> is an integer numbered from zero with no gaps. For some languages and some coding styles, there will only be one block (index value zero) on any particular line.
<branch> is a string which serves to uniquely identify a particular edge. For some languages and tools - e.g., C/C++ code compiled with gcc or llvm - <branch> is an ordered integer index related to expression tree traversal order of the associated conditional. For others, it may be a meaningful string - see below. <branch> appears in the 'tooltip' popup of the associated branch in the genhtml output - so human-readable values are helpful to users who are trying to understand coverage results - for example, in order to develop additional regression tests, to improve coverage.
<taken> is either '-' if the corresponding expression was never evaluated (e.g., the basic block containing the branch was never executed) or a number indicating how often that branch was taken.
<exception> is 'e' (single character) if this is a branch related to exception handling - and is not present if the branch is not related to exceptions. Exception branch identification requires compiler support; note that gcc versions older than 9 do not differentiate exception branches. Geninfo will be able to identify exception branches only if your toolchain version is new enough to support the feature. The following are example branch records whose <branch> expression values are human-readable strings.
      BRDA:10,0,enable,1
      BRDA:10,0,!enable,0
In this case, the corresponding code from line 10 is very likely similar to:
       if (enable) {
         ...
       }
such that the associated testcase entered the block ('enable' evaluated to 'true'). Arbitrarily complicated branch expressions are supported - including branch expressions which contain commas ( e.g.,
 in an expression containing a function call). Note that particular tools may or may not suppress expressions which are statically true or statically false - e.g., expressions using template parameters. This makes it potentially complicated to compare coverage data generated by two different tools. Branch coverage summaries are stored in two lines:
    BRF:<number of branches found>
    BRH:<number of branches hit>
MC/DC information is stored one line per expression:
    MCDC:<line_number>,<groupSize>,<sense>,<taken>,<index>,<expression>
where: <line_number> is the line number where the condition is found - and is expected to be a non-zero integer.
<groupSize> and <index> serve to uniquely define a particular element in the expression tree of a particular conditional found on the associated line.
Within a particular line and group, <index> is an integer numbered from zero to <groupSize> - 1 with no gaps. For some languages and some coding styles, there will only be one group on any particular line. <sense> is either f or t , indicating whether the condition is sensitive to the indicated change - that is, does the condition outcome change if the corresponding changes from 'false' to 'true' or from 'tru' to 'false, respectively. <taken> is a count - 0 (zero) if the expression was not senstized, non-zero if it was senstized. Note that tome tools may treat <taken> as the number of times that the expression was sensitized where others may treat it as a boolean - 1:sensitized or 0: not sensitized. <expression> is an arbitrary string, intended to be a meaningful string which will help the user to understand the condition context - see below. <expression> appears in the 'tooltip' popup of the associated MC/DC condition in the genhtml output - so human-readable values are helpful to users who are trying to understand coverage results - for example, in order to develop additional regression tests, to improve coverage.
For a given <groupSize> and <index>, the <expression> should be identical for both "t" and "f" senses. The following are example MC/DC records whose <expression> values are human-readable strings.
      MCDC:10,2,f,0,0,enable
      MCDC:10,2,t,1,0,enable
      ...
In this case, the corresponding code from line 10 is very likely similar to:
       if (enable ...) {
         ...
       }
such that the associated testcase was sensitive to a change of 'enable' from true to false (but not the converse). Arbitrarily complicated expressions are supported - including expressions which contain commas ( e.g.,
 in an expression containing a function call). Note that particular tools may or may not suppress expressions which are statically true or statically false - e.g., expressions using template parameters. This makes it potentially complicated to compare coverage data generated by two different tools. MCDC coverage summaries are stored in two lines:
    MRF:<number of conditions found>
    MRH:<number of condition hit>
Then there is a list of execution counts for each instrumented line (i.e. a line which resulted in executable code):
    DA:<line number>,<execution count>[,<checksum>]
Note that there may be an optional checksum present for each instrumented line. The current geninfo implementation uses an MD5 hash as checksumming algorithm. At the end of a section, there is a summary about how many lines were found and how many were actually instrumented:
    LH:<number of lines with a non-zero execution count>
    LF:<number of instrumented lines>
Each sections ends with:
    end_of_record
In addition to the main source code file there are sections for all #included files which also contain executable code. Note that the absolute path of a source file is generated by interpreting the contents of the respective .gcno file (see gcov (1) for more information on this file type). Relative filenames are prefixed with the directory in which the .gcno file is found. Note also that symbolic links to the .gcno file will be resolved so that the actual file path is used instead of the path to a link. This approach is necessary for the mechanism to work with the /proc/gcov files.

FILES
/etc/lcovrc
    The system-wide configuration file.
~/.lcovrc
    The per-user configuration file.
/opt/local/share/lcov//support-scripts/getp4version
    Sample script for use with --version-script that obtains version IDs via Perforce.
/opt/local/share/lcov//support-scripts/get_signature
    Sample script for use with --version-script that uses md5hash as version IDs.

AUTHOR
Peter Oberparleiter <Peter.Oberparleiter@de.ibm.com> Henry Cox <henry.cox@mediatek.com>
    Filtering, error management, parallel execution sections.

SEE ALSO
lcov(1), lcovrc(5), genhtml(1), genpng(1), gendesc(1), gcov(1)
https://github.com/linux-test-project/lcov