GCOV-TOOL(1)			      GNU			  GCOV-TOOL(1)


NAME
       gcov-tool - offline gcda profile processing tool

SYNOPSIS
       gcov-tool [-v|--version] [-h|--help]

       gcov-tool merge [merge-options] directory1 directory2
	    [-o|--output directory]
	    [-v|--verbose]
	    [-w|--weight w1,w2]

       gcov-tool merge-stream [merge-stream-options] [file]
	    [-v|--verbose]
	    [-w|--weight w1,w2]

       gcov-tool rewrite [rewrite-options] directory
	    [-n|--normalize long_long_value]
	    [-o|--output directory]
	    [-s|--scale float_or_simple-frac_value]
	    [-v|--verbose]

       gcov-tool overlap [overlap-options] directory1 directory2
	    [-f|--function]
	    [-F|--fullname]
	    [-h|--hotonly]
	    [-o|--object]
	    [-t|--hot_threshold] float
	    [-v|--verbose]

DESCRIPTION
       gcov-tool is an offline tool to process gcc's gcda profile files.

       Current gcov-tool supports the following functionalities:

       *   merge two sets of profiles with weights.

       *   read a stream of profiles with associated filenames and merge it
	   with a set of profiles with weights.

       *   read one set of profile and rewrite profile contents. One can scale
	   or normalize the count values.

       Examples of the use cases for this tool are:

       *   Collect the profiles for different set of inputs, and use this tool
	   to merge them. One can specify the weight to factor in the relative
	   importance of each input.

       *   Collect profiles from target systems without a filesystem
	   (freestanding environments).	 Merge the collected profiles with
	   associated profiles present on the host system.  One can specify
	   the weight to factor in the relative importance of each input.

       *   Rewrite the profile after removing a subset of the gcda files,
	   while maintaining the consistency of the summary and the histogram.

       *   It can also be used to debug or libgcov code as the tools shares
	   the majority code as the runtime library.

       Note that for the merging operation, this profile generated offline may
       contain slight different values from the online merged profile. Here
       are a list of typical differences:

       *   histogram difference: This offline tool recomputes the histogram
	   after merging the counters. The resulting histogram, therefore, is
	   precise. The online merging does not have this capability -- the
	   histogram is merged from two histograms and the result is an
	   approximation.

       *   summary checksum difference: Summary checksum uses a CRC32
	   operation. The value depends on the link list order of gcov-info
	   objects. This order is different in gcov-tool from that in the
	   online merge. It's expected to have different summary checksums. It
	   does not really matter as the compiler does not use this checksum
	   anywhere.

       *   value profile counter values difference: Some counter values for
	   value profile are runtime dependent, like heap addresses. It's
	   normal to see some difference in these kind of counters.

OPTIONS
       -h
       --help
	   Display help about using gcov-tool (on the standard output), and
	   exit without doing any further processing.

       -v
       --version
	   Display the gcov-tool version number (on the standard output), and
	   exit without doing any further processing.

       merge
	   Merge two profile directories.

	   -o directory
	   --output directory
	       Set the output profile directory. Default output directory name
	       is merged_profile.

	   -v
	   --verbose
	       Set the verbose mode.

	   -w w1,w2
	   --weight w1,w2
	       Set the merge weights of the directory1 and directory2,
	       respectively. The default weights are 1 for both.

       merge-stream
	   Collect profiles with associated filenames from a gcfn and gcda
	   data stream.	 Read the stream from the file specified by file or
	   from stdin.	Merge the profiles with associated profiles in the
	   host filesystem.  Apply the optional weights while merging
	   profiles.

	   For the generation of a gcfn and gcda data stream on the target
	   system, please have a look at the "__gcov_filename_to_gcfn()" and
	   "__gcov_info_to_gcda()" functions declared in "#include <gcov.h>".

	   -v
	   --verbose
	       Set the verbose mode.

	   -w w1,w2
	   --weight w1,w2
	       Set the merge weights of the profiles from the gcfn and gcda
	       data stream and the associated profiles in the host filesystem,
	       respectively.  The default weights are 1 for both.

       rewrite
	   Read the specified profile directory and rewrite to a new
	   directory.

	   -n long_long_value
	   --normalize <long_long_value>
	       Normalize the profile. The specified value is the max counter
	       value in the new profile.

	   -o directory
	   --output directory
	       Set the output profile directory. Default output name is
	       rewrite_profile.

	   -s float_or_simple-frac_value
	   --scale float_or_simple-frac_value
	       Scale the profile counters. The specified value can be in
	       floating point value, or simple fraction value form, such 1, 2,
	       2/3, and 5/3.

	   -v
	   --verbose
	       Set the verbose mode.

       overlap
	   Compute the overlap score between the two specified profile
	   directories.	 The overlap score is computed based on the arc
	   profiles. It is defined as the sum of min (p1_counter[i] /
	   p1_sum_all, p2_counter[i] / p2_sum_all), for all arc counter i,
	   where p1_counter[i] and p2_counter[i] are two matched counters and
	   p1_sum_all and p2_sum_all are the sum of counter values in profile
	   1 and profile 2, respectively.

	   -f
	   --function
	       Print function level overlap score.

	   -F
	   --fullname
	       Print full gcda filename.

	   -h
	   --hotonly
	       Only print info for hot objects/functions.

	   -o
	   --object
	       Print object level overlap score.

	   -t float
	   --hot_threshold <float>
	       Set the threshold for hot counter value.

	   -v
	   --verbose
	       Set the verbose mode.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), gcc(1), gcov(1) and the Info entry for
       gcc.

COPYRIGHT
       Copyright (c) 2014-2025 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3 or
       any later version published by the Free Software Foundation; with the
       Invariant Sections being "GNU General Public License" and "Funding Free
       Software", the Front-Cover texts being (a) (see below), and with the
       Back-Cover Texts being (b) (see below).	A copy of the license is
       included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

	    A GNU Manual

       (b) The FSF's Back-Cover Text is:

	    You have freedom to copy and modify this GNU Manual, like GNU
	    software.  Copies published by the Free Software Foundation raise
	    funds for GNU development.

gcc-15.2.1			  2025-08-13			  GCOV-TOOL(1)