Add meson build support

[jianhe-fun]

hi.
any plan to use meson build instead of cmake?
https://mesonbuild.com/

[carenas]

instead of cmake?

I don't think meson support in Windows is good enough to "replace" cmake (which is also foundational for other build systems), but there is a Meson wrap that I had contributed to and are overdue on updating that could be used instead AFAIK.

[NWilson]

We don't have plans for Meson currently.

Each of our current supported build systems is there for a reason.

• Autoconf: required for old Unix platforms (commercial) without CMake (rare these days)
• CMake: required for good IDE support, Windows support, generally most-used. Required for us to supply a CMakeLists.txt so that C/C++ package managers like vcpkg or Conan can consume PCRE2
• Zig: it's a separate language, makes sense it needs its own magic (sadly)
• Bazel: This one is the outlier. It's incredibly opinionated. You can't shell out to a third-party build system from Bazel, we have to supply a native Bazel build for those clients

In Meson, can you not incorporate a CMake dependency by invoking CMake on it? CMake is so dominant, there must be a pattern for consuming libraries with pkg-config, or CMake config files?

What advantage would there be for you? Unless you need it, we probably won't add it.

[NWilson]

@jianhe-fun Do you have any further details as requested on why you need Meson support, rather than using Meson's support for CMake, or the existing Meson wrap mentioned by Carlo?

[jianhe-fun]

seems many other open source tool also use meson. I don't any specific issue with this library.
we can close this issue.

[NWilson]

Thank you for explaining.

@carenas Do you know who created the Meson wrap file? It looks quite fully-featured.

I'm reluctant to add yet another build system to our supported list. However, if people on Meson do need to build PCRE2 in this custom way, then it probably makes sense to just accept their Meson file upstream in our project, so it doesn't bitrot.

Is Meson hard to learn, in terms of all the annoying details? I spent a lot of time on CMake in the last year, but hopefully, everything is modernised now, and I won't need to touch CMake again for a while.

[carenas]

@carenas Do you know who created the Meson wrap file? It looks quite fully-featured.

It is a community effort, and it is being used at least by git that is transitioning its build system from GNU Makefile to Meson, hence why I got involved on its development as well.

Meson seems simpler to maintain than CMake IMHO, as the syntax is very straight forward and Python like, and very well documented, but if we are going to import the wrap, I would rather use the improved version I have, which I haven't been able to contribute back yet and that fixes several important issues the current wrap has.

[NWilson]

OK. Git is a high-profile customer of PCRE2, so, if they use an externally-maintained Meson build file for PCRE2, I would see that as a good reason to make it officially-supported. That way we can ensure that we don't break the Meson build when we make new releases.

I wouldn't rush to do it though. No need to get it into the next release - we're probably still going to receive feedback on the CMake changes in 10.45/47, when people finish updating to those.

[jianhe-fun]

hi. Postgres (database) use meson, some of the postgres extension also use meson.
the meson community seems pretty good.

as for PCRE2, i found the coding style seems very different from postgres.
I kind of give up trying to read the source code.
even though i am interested in regular expression.