testland/embedded-coverage-strategy-reference
Pure-reference catalog of code-coverage strategy for embedded C/C++: the criteria hierarchy (statement / branch / decision / condition / MC/DC), the gcov toolchain (.gcno/.gcda, --coverage), the LLVM source-based toolchain (llvm-profdata / llvm-cov), host-build vs QEMU-build instrumentation, MISRA-C:2012 and DO-178C structural-coverage expectations by safety level (DAL A maps to MC/DC), and report-format choices. Use when choosing what structural-coverage level to require and wiring gcov / llvm-cov into the build; physical .gcda retrieval from hardware is in hardware-in-loop-reference, QEMU machine flags in qemu-system-test-runner, and to author the embedded tests themselves use googletest-embedded-arm or unity-test-framework-c.
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safety-standards-and-formats.mdreferences/
Safety-standard coverage expectations and report formats
Deep reference for the embedded-coverage-strategy-reference SKILL.md.
Consult when negotiating a coverage target against a safety standard, or when
choosing which report format to produce and gate on.
Safety-standard coverage expectations
These are cited by stable ID - the standards themselves are gated and not WebFetchable.
| Standard / level | Minimum structural coverage |
|---|---|
| MISRA-C:2012 Coverage Guidance | No prescribed numeric target; the rule set requires defined control flow and explicit default: in switch, which makes branch coverage achievable. See "MISRA-C:2012 §8 Coverage" |
| DO-178C / DAL A (catastrophic failure) | MC/DC required for every condition (see "DO-178C §6.4.4 Structural Coverage") |
| DO-178C / DAL B | Decision coverage |
| DO-178C / DAL C | Statement coverage |
| DO-178C / DAL D | None mandated |
| ISO 26262 ASIL D | MC/DC strongly recommended for unit verification (see "ISO 26262-6:2018 Table 12") |
| ISO 26262 ASIL A / B / C | Branch (B/C) or statement (A) coverage |
| IEC 62304 Class C (medical, life-supporting) | No numeric target, but bidirectional traceability + structural coverage justification expected |
The number "100% MC/DC" in aviation is famously expensive; the standard accepts "MC/DC of the integrated executable object code" which is interpreted differently by certifiers. Treat these as the floor, not a turnkey recipe.
Coverage report formats
| Format | Producer | Consumer |
|---|---|---|
.gcov (text) | gcov | Human reading; line-level annotation |
.gcov.json.gz | gcov --json-format | CI parser; no source-code dependency per GCC docs |
.info (LCOV) | lcov --capture or llvm-cov export -format=lcov | Codecov / Coveralls / SonarQube |
.profdata | llvm-profdata merge | Input only to llvm-cov |
| HTML | genhtml (LCOV) or llvm-cov show -format=html | Humans; not for diff'ing |
| JSON | llvm-cov export -format=text | Custom CI dashboards |
| Cobertura XML | gcovr --xml (gcovr is a third-party gcov wrapper) | Jenkins coverage plugin |
For embedded CI, the rule of thumb is: produce lcov.info as the durable
artefact; render HTML for the developer; gate the PR on the .info totals.