fixes #23668; migrates from pcre to pcre2

[ringabout]

fixes #23668

Most of tre.nim and tnre.nim passed and didn't leak when checked with valgrind.

TODO

• Clean up + JIT support
• Figure out how to solve some incompatibility because of the transition from pcre to pcre2 (some options are deprecated; UTF-8 and Unicode support etc.)
• Improve code shape
• Ship necessaries DLLs on Windows

Useful links

PCRE2Project/pcre2#51 (comment)

php/php-src#2857

i3/i3#4682 (comment)

https://copilot.microsoft.com

[arnetheduck]

shouldn't this be the version of the dynamically loaded pcre2 library? the version on the OS might be anything, including much older ones?

[ringabout]

How to load a C define from a dynamic library?

#define PCRE2_MAJOR           @PCRE2_MAJOR@
#define PCRE2_MINOR           @PCRE2_MINOR@
#define PCRE2_PRERELEASE      @PCRE2_PRERELEASE@
#define PCRE2_DATE            @PCRE2_DATE@

[arnetheduck]

libraries usually have a function for that, to load it dynamically - even if you compile on one system, another system you run the compiled binary will have a different version making these defines entirely meaningless at best

[nileshpatra]

@ringabout the pcre2_config API from pcre2 can help you get the version dynamically (at run time).

@arnetheduck I see the same hard-coding done in pcre.nim as well, see https://github.com/nim-lang/Nim/blob/devel/lib/wrappers/pcre.nim#L13

Why was that not a problem but hardcoding here is a problem? Is that because of the fact that there was no active development happening on pcre1?

[arnetheduck]

Why was that not a problem but hardcoding here is a problem?

It's a problem no matter the pcre version but this line of reasoning might not have been understood at the time of writing the pcre module either and indeed, the fact that pcre1 is dead contributed to the downstream issues not manifesting practically. The best outcome here is perhaps to deprecate these symbols (or indeed, deprecate the whole pcre module) because any code using them will have been "infected" by this gap in reasoning about what they represent.