Add a "system" dependency for zlib

[dcbaker]

This adds a system depenedency for zlib, so that platforms that ship zlib as part of the base os (macOS, FreeBSD, and probably other BSDs but I don't have VMs for all of them). This allows zlib to be found without the use of cmake of pkg-config, which is especially helpful on macOS.

This has been updated on top of #6443

Fixes #2654

[xclaesse]

It is not limited to macosx/bsd, for example when cross compiling for Android NDK it also have the zlib but no pkg-config file. For example, here is how GLib search for zlib: https://gitlab.gnome.org/GNOME/glib/blob/master/meson.build#L1872. This is the kind of mess I'm trying to solve with #4595.

That being said, I guess macosx/freebsd are popular enough to have their special case until we have a fully-fledged solution.

[dcbaker]

I wouldn't want to do this for every dependency, but zlib is really popular so having a built-in solution seems better to me.

[scivision]

I have added several dependencies like this, and would eventually add numerous more, because of the frequent imperfection in packages' pkg-config files and other corner cases. Another choice would be to lean heavily on CMake inside Meson, since CMake has typically already solved the corner cases.

[jpakkane]

  File "D:\a\1\s\mesonbuild\dependencies\base.py", line 2206, in find_external_dependency
    candidates = _build_external_dependency_list(name, env, kwargs)
  File "D:\a\1\s\mesonbuild\dependencies\base.py", line 2281, in _build_external_dependency_list
    dep = packages[lname]._factory(env, kwargs)
  File "D:\a\1\s\mesonbuild\dependencies\misc.py", line 377, in _factory
    methods = cls._process_method_kw(kwargs)
TypeError: _process_method_kw() missing 1 required positional argument: 'kwargs'

[dcbaker]

Yup. I've got another series that cleans up a lot of cruft in the dependencies (mostly in the dependencies that have > 1 way to find them) that I think should land before this, but isn't done. Consider this on hold until then.

[nirbheek]

There's two more corner-cases that should probably go in here: the library is sometimes called zlib.lib and sometimes zlib1.lib: https://gitlab.gnome.org/GNOME/glib/blob/master/meson.build#L1872

[dcbaker]

@nirbheek

There's two more corner-cases that should probably go in here: the library is sometimes called zlib.lib and sometimes zlib1.lib: https://gitlab.gnome.org/GNOME/glib/blob/master/meson.build#L1872

That code seems to have been (re)moved. I'm assuming (based on .lib) that's for windows?

[xclaesse]

@dcbaker it's just a few lines down:

# Don't use the bundled ZLib sources until we are sure that we can't find it on
# the system
libz_dep = dependency('zlib', required : false)
if not libz_dep.found()
  if cc.get_id() != 'msvc' and cc.get_id() != 'clang-cl'
    libz_dep = cc.find_library('z', required : false)
  else
    libz_dep = cc.find_library('zlib1', required : false)
    if not libz_dep.found()
      libz_dep = cc.find_library('zlib', required : false)
    endif
  endif
  if not libz_dep.found() or not cc.has_header('zlib.h')
    libz_dep = subproject('zlib').get_variable('zlib_dep')
  endif
endif

[dcbaker]

Okay, added windows, added a test case. lets see what happens.

[dcbaker]

Okay off hold, @xclaesse, does this look good?

[scivision]

I have not tried to use Zlib from Windows. So this may be just a fluke test result. Here's what I got from VS 2019:

> meson build

The Meson build system
Version: 0.53.999
Source dir: meson\test cases\common\228 zlib
Build dir: meson\test cases\common\228 zlib\build
Build type: native build
Project name: zlib system dependency
Project version: undefined
C compiler for the host machine: cl (msvc 19.24.28314)
C linker for the host machine: link link 14.24.28314.0
Host machine cpu family: x86_64
Host machine cpu: x86_64
Library z found: NO
Library zlib found: NO
Library zlib1 found: NO

meson.build:19:2: ERROR: Problem encountered: MESON_SKIP_TEST Cannot seem to find zlib via find_library, this test will probably fail.

[dcbaker]

I'm not sure how @nirbheek and @xclaesse are installing zlib on windows, it's not part of the base OS AFAICT

[scivision]

OK then disregard my result from VS 2019, thanks

[jpakkane]

LGTM.

[lantw44]

This adds a system depenedency for zlib, so that platforms that ship zlib as part of the base os (macOS, FreeBSD, and probably other BSDs but I don't have VMs for all of them).

In fact, FreeBSD provides zlib.pc as a part of the OS since 10.1 release: https://svnweb.freebsd.org/changeset/base/267376. Since all FreeBSD releases without zlib.pc are EOL, it should be safe to say that zlib.pc is always available on FreeBSD.