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Ferroni

POSIX and GNU API Not Ported

Status

Accepted

Context

C Oniguruma includes three compatibility layers:

  • regposix.c (~300 LOC): POSIX regcomp/regexec/regfree/regerror API wrapper
  • regposerr.c (~100 LOC): POSIX error message strings
  • reggnu.c (~100 LOC): GNU regex compatibility (re_compile_pattern, re_search, etc.)

These exist so that C programs using the standard POSIX or GNU regex interfaces can be linked against Oniguruma as a drop-in replacement.

Decision

None of these compatibility layers are ported.

Rationale

  • No use case in Rust. The POSIX regex API (<regex.h>) is a C-world interface. Rust programs do not call regcomp/regexec -- they use Rust-native APIs. The Oniguruma API (onig_new/onig_search) is the native interface and is fully ported.
  • The GNU API is equally irrelevant. re_compile_pattern and friends are GNU extensions to the POSIX API, used in C programs like grep. Same reasoning applies.
  • The associated test suite (testp.c, 421 tests) tests the POSIX wrapper, not the engine. Skipping it does not reduce engine test coverage.

Consequences

  • C programs that use Oniguruma through the POSIX API cannot migrate to this Rust port without changing their regex interface calls.
  • This is consistent with ADR-003 (encoding scope) -- both decisions reduce the porting surface to what is actually useful in a Rust context.