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

• Detect build system (Makefile/CMake/other)

• Add --coverage to CFLAGS and LDFLAGS

• Clean previous build: make clean or rm -f *.gcda *.gcno

• Build with coverage: make ENABLE_COVERAGE=1 or cmake -DENABLE_COVERAGE=ON

• Run tests: make test or ./test_suite

• Generate report: gcovr --html-details coverage.html --print-summary

• 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