Gcov

Gcov is a code coverage analysis tool provided with the GNU Compiler Collection (GCC). It measures how often each line of code, decision, and branch is executed when a program runs.

Gcov helps developers and testers understand which parts of the source code were executed during testing and which parts were not.

To do this, Gcov works by compiling the software with instrumentation enabled. This instrumentation inserts counters into the executable that record execution data during a test run.

After execution, Gcov generates coverage reports showing:

• Line coverage

• Branch coverage

• Function coverage

In functional safety projects, this information is used to demonstrate that testing has exercised the software logic thoroughly and systematically.

Structural code coverage is a mandatory verification activity in ISO 26262.

ISO 26262 uses code coverage metrics to judge whether software testing is sufficiently complete to uncover systematic faults.

According to ISO 26262‑6, the required coverage depth increases with the Automotive Safety Integrity Level (ASIL):

• Lower ASILs may accept statement or line coverage

• Higher ASILs (ASIL C and ASIL D) require branch coverage or MC/DC

Structural coverage provides objective evidence that:

• All implemented logic has been executed

• No hidden or dormant code paths remain untested

• No additional functionality without requirements

If Gcov incorrectly reports complete coverage, engineers may falsely assume that safety-critical code has been tested, which can lead to undetected systematic faults.

The primary challenge is the probe effect caused by instrumentation.

Instrumentation with Gcov:

• Increases memory usage

• Alters execution timing and can affect real-time behavior

Engineers must ensure that all tests pass with instrumentation enabled and with instrumentation disabled.

• GNU Compiler Collection – Gcov Documentation Gcov Intro (Using the GNU Compiler Collection (GCC))

• ISO 26262‑6 & ISO 26262‑8 (Road Vehicles – Functional Safety) International Organization for Standardization (ISO), 2018 edition