Path coverage in gcc
summary
GCC adds a new fpath-coverage option to emit GCOV data for prime path coverage aimed at GCC 15 (NASA-funded). It computes prime/simple paths across function CFGs, reports missing path traces, and shows concrete line sequences to exercise each path; binary-search demo has 24 prime paths and runs find cases that move coverage from 0 → 12 → 13 → 16, etc. Path coverage subsumes statement/branch/condition/DU but not MCDC; costs grow (typical 3x compile time and larger objects; extreme case 2m26s build and 32 MB object).
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chapters (15)
- 0:00Path coverage in GCC
- 1:49NASA funding path coverage
- 5:27Coverage metrics limitations
- 10:24Definition-use pairs
- 14:24Program graphs in compilers
- 16:32Path explosion and prime paths
- 23:05GCC 15 path coverage demo
- 35:00Coverage criteria subsumption
- 38:12Coverage and functional testing
- 45:21Binary search with path coverage
- 50:20Impossible paths handling
- 51:02MCDC in complex code
- 54:18Coverage compatibility and fuzzing
- 56:45Prime paths vs MCDC
- 58:10Optimization and coverage
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