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Code Coverage with gcov

Testing & Quality
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Add gcov code coverage instrumentation to C/C++ projects

License unclear

QUICK START

How to use this skill

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  1. Open your project in Codex.
  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
Prompt to paste
I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/gadievron/raptor/blob/HEAD/.claude/skills/crash-analysis/gcov-coverage/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/code-coverage-with-gcov/. Do not write files or run scripts until I approve.

After I approve, install the complete skill folder, including required referenced files, into that project location. Verify it is discoverable, then tell me its actual invocation name and how to use it. Do not claim it is installed until you have verified it.

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Code Coverage with gcov

Purpose

Instrument C/C++ programs with gcov to measure test coverage.

How It Works

Build with Coverage

gcc --coverage -o program source.c

Run Program

./program
# Creates .gcda files with execution data

Generate Reports

Text report:

gcov source.c
# Creates source.c.gcov with line-by-line coverage

HTML report:

gcovr --html-details -o coverage.html

Coverage Flags

  • --coverage (shorthand for -fprofile-arcs -ftest-coverage -lgcov)
  • Add to both CFLAGS and LDFLAGS

Build System Integration

Makefile

ENABLE_COVERAGE ?= 0
ifeq ($(ENABLE_COVERAGE),1)
    CFLAGS += --coverage
    LDFLAGS += --coverage
endif

CMake

option(ENABLE_COVERAGE "Enable coverage" OFF)
if(ENABLE_COVERAGE)
    add_compile_options(--coverage)
    add_link_options(--coverage)
endif()

When User Requests Coverage

Steps

  1. Detect build system (Makefile/CMake/other)
  2. Add --coverage to CFLAGS and LDFLAGS
  3. Clean previous build: make clean or rm -f *.gcda *.gcno
  4. Build with coverage: make ENABLE_COVERAGE=1 or cmake -DENABLE_COVERAGE=ON
  5. Run tests: make test or ./test_suite
  6. Generate report: gcovr --html-details coverage.html --print-summary
  7. Present summary and path to HTML report

Output

Text (.gcov files):

        -:    0:Source:main.c
        5:   42:    int x = 10;
    #####:   43:    unused_code();
  • 5: = executed 5 times
  • #####: = not executed
  • -: = non-executable

HTML: Interactive report with color-coded coverage

Metrics

  • Line coverage: Executed lines / total lines
  • Branch coverage: Taken branches / total branches
  • Function coverage: Called functions / total functions

Target: 80%+ line coverage, 70%+ branch coverage