[danmar]

Replace the discontinued PCRE library with PCRE2 for rules

PCRE (8.x) is end of life and is being removed from Linux distributions.

• lib/regex.cpp: use the PCRE2 API (with JIT when available)
• fix endless loop when a rule pattern matches an empty string
• CMake, Makefile, dmake and Visual Studio project use PCRE2
• CI installs/builds PCRE2 instead of PCRE
• update documentation

Rule files and the "pcre" engine name are unchanged.

[danmar]

@fliiiix @andrew-aitchison @loqs @Harvester57 @pfultz2 @firewave
this PR replaces PCRE with PCRE2.
So it's more aggressive than #8382 .
I have implemented this with AI so any help with reviewing / testing it out would be appreciated.

[dmcppcheck]

AI review

I found no new problems. lib/regex.cpp now uses the PCRE2 API correctly. The match data is created on each call, so a Regex that several threads share is safe. A failed JIT compile falls back to the interpreter. The match loop steps forward one byte after an empty match, so patterns such as b* or ( x)? no longer loop forever. Error messages for patterns that do not compile are the same as before (\ at end of pattern, missing terminating ] for character class), so the existing expected strings in the tests still pass. Patterns that match an empty string now report a found '' finding at many positions. Cppcheck's de-duplication cuts that down to one per line, and the same behaviour lets zero-width rules such as (?= x) work, so I don't count it as a defect. I could not check the Windows/MSVC and CI changes (library names, install prefix) here.

Testing

Build: The container has the libpcre2-8 runtime (10.42, libpcre2-8.so.0) but no headers and no pcre2-config. To build anyway, I wrote a small pcre2.h that declares only the functions regex.cpp uses (they map to the _8 symbols), plus a fake pcre2-config (--cflags/--libs8). With those I built make -j8 HAVE_RULES=yes cppcheck testrunner in pr/, and it built without errors. Base was not built: PCRE1 is not available, so I could not compare against the old engine.

Unit tests: ./testrunner TestRegExPcre TestCmdlineParser TestCppcheck ran 406 tests with 0 failures, including the new emptymatch and the compile-error message checks in TestCmdlineParser.

Python tests: pytest rules_test.py gave 6 passed. pytest other_test.py helloworld_test.py inline-suppress-polyspace_test.py -k rule gave 6 passed.

Manual checks with cppcheck --rule=... on a small C file:

• ( x)? (matches the empty string) finishes at once. It reports the empty matches, which are de-duplicated to one per line, as well as the real x matches.
• (?= x) (zero-width lookahead) reports the right lines.
• \bx\b gives correct results, so word boundaries work when matching starts partway into the string.
• Running on 30 files with -j8 and an empty-matching rule finishes with stable output and no hang.
• (?<=x gives failed to compile rule pattern '(?<=x' (missing closing parenthesis).
• A pattern that recurses without end, (a|aa)*+(?:(?R)), gives the error JIT stack limit reached (pos: 0) [pcre_exec] instead of crashing or hanging.

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Automated review of ab7764c by Claude. The pull request was built and tested locally.

[Harvester57]

Hi there,

Built and tested locally by cherry-picking the PR over v2.22.0, applies cleanly and works perfectly well, thank you very much !