host zlib is found using a cross file.

Describe the bug When using a cross file which is not setting pkg_config_libdir, meson find the host version of zlib with

MESON build-cross --cross-file=path_to/my-cross-file.txt

To Reproduce

Meson file:

project('hellomeson', 'c')
cc = meson.get_compiler('c')
libz_dep = dependency('zlib', required : false)
if not libz_dep.found()
warning('unable to find libz')
endif
executable('hello-meson', 'src/hello.c')

Cross file:

[host_machine]
system = 'linux'
cpu_family = 'aarch64'
cpu = 'arm64'
endian = 'little'

[properties]
c_args = []
cpp_args = []
objc_args = []
objcpp_args = []
c_link_args = []
cpp_link_args = []
objc_link_args = []
objcpp_link_args = []
pkg_config_libdir = ['__unknown_sysroot__']


[binaries]
c = ['aarch64-linux-gnu-gcc']
cpp = ['aarch64-linux-gnu-g++']
ar = ['aarch64-linux-gnu-ar']
pkgconfig = 'pkg-config'
strip = ['aarch64-linux-gnu-strip']

Expected behavior To not find any zlib or at least not the one from my host and then use it…

system parameters

• Is this a cross build or just a plain native build (for the same computer)? cross build
• what operating system (e.g. MacOS Catalina, Windows 10, CentOS 8.0, Ubuntu 18.04, etc.) Ubuntu 18.04
• what Python version are you using e.g. 3.8.0 3.6.9
• what meson --version master
• what ninja --version if it’s a Ninja build 1.8.2

[mensinda]

Should be fixed with #8096.

I opted for reverting to the old behavior since I couldn’t find a solution based on CMake variables that should do the correct thing in all circumstances.

[mensinda]

I think we should not have to specify anything about cmake in the cross-compilation file, given we should not use cmake.

Sorry, but this is wrong. CMake is a valid dependency backend in meson (just like pkg-config) and also capable of finding cross dependencies. However, it is sadly not correctly setup out of the box currently, resulting in this error.

And I don’t understand how we are supposed to workaround it?

What should we do?

Using the setup in https://github.com/mesonbuild/meson/issues/8028#issuecomment-734360181 to set the CMake variables (wich should cause CMake to behave correctly) should work for now if disabling CMake in the cross file doesn’t work for some reason.

Also, to clarify, I agree that this is a valid issue and the current behavior should be fixed, I only disagree with using a cross CMake binary. The solution I would prefer is to set these variables automatically for the cross-case for the next point release, which should also fix the issue.