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C Coding Standard

wolfTrust adheres to the wolfSSL coding standards and targets ISO C99, with project-specific no-goto and no-standalone-scope rules. The aim is to keep the code straightforward to assess in a future MISRA C:2023 or DO-178 process. These checks improve readiness; they are not a claim of MISRA compliance or certification evidence.

Required rules

  • Compile project C as ISO C99. Variable-length arrays are prohibited.
  • Do not use goto. Use structured control flow and status-gated fallthrough cleanup.
  • Do not use standalone brace blocks solely to shorten a variable's lifetime.
  • Use C comments (/* ... */), spaces in core source, and no trailing whitespace. Preserve existing section-banner style when editing nearby code.
  • Explicitly erase sensitive buffers that must be cleared. Existing secure- erasure routines use volatile byte writes; record that approach as a deviation in any formal MISRA compliance plan.
  • Use WT_STATIC_ASSERT() for file-scope compile-time checks; _Static_assert is C11 and is not permitted.

Runnable tests follow the no-goto and no-standalone-scope rules. Vendored submodules keep their upstream coding standards. The pinned wolfHSM callback ABI requires anonymous aggregate support in dependency headers; formal qualification must record that boundary as a dependency deviation. The strict C99 host gate does not compile ARM-only source; target inline assembly and compiler intrinsics require separate platform qualification.

Automated checks

  • sh scripts/check_house_style.sh
  • python3 scripts/check-empty-brace-scopes.py
  • make c99-check CC=clang or make c99-check CC=gcc

The C99 check first compiles a valid C99 probe and verifies that the compiler rejects C11-only syntax and variable-length arrays. It then builds and runs the existing host suites with strict C99 flags.

The matching GitHub Actions workflows run these gates on every pull request.