GCOV-TOOL(1)

GCOV-TOOL(1) 🎀 okay bestie, this is the manual page for gcov-tool from GNU, and it's a whole vibe 💅

✨ NAME ✨

gcov-tool - offline gcda profile processing tool 🦋

🌸 SYNOPSIS 🌸

Here's how you call it, bestie:

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 💅

okay so gcov-tool is an offline tool for processing gcc's gcda profile files, and it is literally that and nothing else 💖

rn it can do three things:

• 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 the profile contents. You can scale or normalize the count values 🔥

Use cases? Iconic, honestly:

• Collect profiles for different sets of inputs, then merge them together. You can give each one a weight to show how important it is 🎀
• Collect profiles from target systems without a filesystem (freestanding environments). Then merge those with the matching profiles on the host system. Weights work here too 🧚
• Rewrite the profile after removing a subset of the gcda files, while keeping the summary and histogram consistent 🍓
• It can also help you debug libgcov code, since the tool shares most of its code with the runtime library 🙈

ngl, an offline merge might come out with slightly different values than the online merged profile. Here are the typical differences, bestie 🫶

• histogram difference: This offline tool recomputes the histogram after merging the counters, so the resulting histogram is precise. The online merge doesn't have this ability. Its histogram gets merged from two histograms, so the result is an approximation 📊
• summary checksum difference: The summary checksum uses a CRC32 operation. The value depends on the link list order of gcov-info objects. That order is different in gcov-tool than in the online merge, so you should expect different summary checksums. It doesn't really matter, though, because the compiler doesn't use this checksum anywhere 🤷‍♀️
• value profile counter values difference: Some value profile counters depend on runtime stuff, like heap addresses. So it's totally normal to see differences in these kinds of counters 🌈

🦋 OPTIONS 🦋

• -h, --help — Shows help about using gcov-tool on the standard output, then exits without doing any further processing 💁‍♀️
• -v, --version — Shows the gcov-tool version number on the standard output, then exits without doing any further processing 🌸
• merge — Merges two profile directories 🔮
  • -o directory, --output directory — Sets the output profile directory. The default output directory name is merged_profile 📁
  • -v, --verbose — Turns on verbose mode 📣
  • -w w1,w2, --weight w1,w2 — Sets the merge weights for directory1 and directory2, respectively. Both default to 1 💜
• merge-stream — Collects profiles with associated filenames from a gcfn and gcda data stream. It reads the stream from the file specified by file or from stdin, then merges the profiles with the associated profiles in the host filesystem. You can apply the optional weights while merging 🌊
  • For generating a gcfn and gcda data stream on the target system, check out the "__gcov_filename_to_gcfn()" and "__gcov_info_to_gcda()" functions declared in "#include <gcov.h>" 🧚
  • -v, --verbose — Turns on verbose mode 📣
  • -w w1,w2, --weight w1,w2 — Sets the merge weights for the profiles from the gcfn and gcda data stream and for the associated profiles in the host filesystem, respectively. Both default to 1 💖
• rewrite — Reads the specified profile directory and rewrites it to a new directory 🍓
  • -n long_long_value, --normalize <long_long_value> — Normalizes the profile. The value you pass is the max counter value in the new profile 🔥
  • -o directory, --output directory — Sets the output profile directory. The default output name is rewrite_profile 📁
  • -s float_or_simple-frac_value, --scale float_or_simple-frac_value — Scales the profile counters. The value can be a floating point value or a simple fraction, like 1, 2, 2/3, and 5/3 ✨
  • -v, --verbose — Turns on verbose mode 📣
• overlap — Computes the overlap score between two specified profile directories. The score is based on the arc profiles, and it's defined as the sum of the following, 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 sums of counter values in profile 1 and profile 2, respectively 🦋

min (p1_counter[i] / p1_sum_all, p2_counter[i] / p2_sum_all)

• -f, --function — Prints the function level overlap score 🎀
• -F, --fullname — Prints the full gcda filename 💅
• -h, --hotonly — Only prints info for hot objects and functions 🔥
• -o, --object — Prints the object level overlap score 🧚
• -t float, --hot_threshold <float> — Sets the threshold for the hot counter value 🌡️
• -v, --verbose — Turns on verbose mode 📣

🌟 SEE ALSO 🌟

gpl(7), gfdl(7), fsf-funding(7), gcc(1), gcov(1) and the Info entry for gcc. Go check them out, bestie 📚

🌈 COPYRIGHT 🌈

Copyright (c) 2014-2024 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. The Invariant Sections are "GNU General Public License" and "Funding Free Software", the Front-Cover texts are (a) (see below), and the Back-Cover Texts are (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."

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That's the whole tea, bestie! 💖 This page came from gcc-14 and is dated 2024-04-12, so go forth and profile responsibly 🫶🌸✨