Getting compiler errors about a missing __COLD attribute? from zig headers

[weiznich]

I have a project that depends on netcdf-src 0.4.0. Trying to build that in the official rust-lang docker container with cargo-zigbuild 0.19.1 and zig 0.13.0 installed fails with the following error messages:

/opt/zig/lib/libc/include/generic-glibc/stdio.h:878:38: error: expected function body after function declarator
    878 | extern void perror (const char *__s) __COLD;
        |                                      ^
  In file included from /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/netcdf-src-0.4.0/source/libdispatch/dcopy.c:11:
  In file included from /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/netcdf-src-0.4.0/source/include/ncdispatch.h:17:
  /opt/zig/lib/libc/include/generic-glibc/stdio.h:878:38: error: expected function body after function declarator
    878 | extern void perror (const char *__s) __COLD;
        |                                      ^
  1 error generated.
  gmake[2]: *** [libsrc/CMakeFiles/netcdf3.dir/build.make:88: libsrc/CMakeFiles/netcdf3.dir/v1hpg.c.o] Error 1
  gmake[2]: *** Waiting for unfinished jobs....
  1 error generated.
// repeated many times

I can workaround that error by just adding CFLAGS="-D__COLD=\"\"" to the compilation environment. I report this here as this either seems to be an issue in cargo-zigbuild (not setting that option) or in zig itself (__COLD) shouldn't be there.

Interestingly it works outside of the docker container with the same rust, zig, zig-build and netcdf-src version…

[messense]

bminor/glibc@0ab341b

It should have been defined by glibc itself (in glibc 2.38+), can you try to inspect the code of the same file in /opt/zig/lib/libc/include/?

[weiznich]

Thanks for the response.

I checked it in the rust docker container and it seem like:

• /opt/zig/lib/libc/include/generic-glibc/sys/cdefs.h does contain the relevant defines
• /usr/include/x86_64-linux-gnu/sys/cdefs.h does not contain the relevant defines

Also ldd reports that the system uses glibc 2.36

It seems like that for some reason the system header from /usr is used and not the bundled header from zig

For reference that's with the rust:1.80.1 docker image (+ a view custom layers to install zig + cargo-zigbuild)

[messense]

Maybe it's caused by cmake? There is support for cmake in cargo-zigbuild but it's not really tested thoroughly.

cargo-zigbuild/src/zig.rs

Lines 475 to 486 in d420792

	let cmake_toolchain_file_env = format!("CMAKE_TOOLCHAIN_FILE_{env_target}");
	if env::var_os(&cmake_toolchain_file_env).is_none()
	&& env::var_os(format!("CMAKE_TOOLCHAIN_FILE_{parsed_target}")).is_none()
	&& env::var_os("TARGET_CMAKE_TOOLCHAIN_FILE").is_none()
	&& env::var_os("CMAKE_TOOLCHAIN_FILE").is_none()
	{
	if let Ok(cmake_toolchain_file) =
	Self::setup_cmake_toolchain(parsed_target, &zig_wrapper, enable_zig_ar)
	{
	cmd.env(cmake_toolchain_file_env, cmake_toolchain_file);
	}
	}

[weiznich]

That might be the case, I'm not sure about that.

As a general note: The project I'm building depends on quite a few complex cmake projects (netcdf, hdf5, gdal, proj, just to name some). It works fine as soon as I specify that additional define manually. I believe that this means the cmake integration should be mostly fine.