Can't find `/usr/lib/libshaderc_shared.so`

[Rua]

I downloaded the pre-built shaderc library package for Linux, and unpacked it in /usr/lib. This is one of the locations where shaderc-rs will search for libraries according to the readme, and /usr/lib/libshaderc_shared.so is right there along with all the other shaderc libraries. Yet for some reason it fails to find the library, and proceeds to build from source (which fails because I uninstalled cmake). How come it's not finding the library? Is the documentation incorrect?

[antiagainst]

Hi, note that /usr/lib/ is just one example given for Linux system library paths: "On Linux, system library paths like ..". There is an implicit ordering in the library path:

shaderc-rs/shaderc-sys/build/build.rs

Lines 180 to 191 in 21bb994

	search_dir = if Path::new(&debian_triple_path).exists() {
	// Debian, Ubuntu and their derivatives.
	Some(debian_triple_path)
	} else if env::var("CARGO_CFG_TARGET_ARCH").unwrap() == "x86_64"
	&& Path::new("/usr/lib64/").exists()
	{
	// Other distributions running on x86_64 usually use this path.
	Some("/usr/lib64/".to_owned())
	} else {
	// Other distributions, not x86_64.
	Some("/usr/lib/".to_owned())
	};

And /usr/lib/ is the last one of it. I think the problem is that only directory existence was checked there; not the library. So as long as you have other directories recognized, they will be picked by the script.

This is all very tricky and ad-hoc. I think the above part should be rewritten to just use some more standardized way to probe system shared libraries.

Hopefully this clarifies.

[nbraud]

This is all very tricky and ad-hoc. I think the above part should be rewritten to just use some more standardized way to probe system shared libraries.

Yes, using pkg-config would be the standard way to solve the problem on (AFAIK) all opensource distros, be it Linux, *BSD, etc.

As it stands, this prevents using prebuilt versions of shaderc on NixOS (or any dev environment managed with nix) as they would be found under /nix/store/{hash}-shaderc-{version}-{dev, lib}/: pkg-config would find them through its environment variables, which are automatically set by a nix setup-hook for pkg-config.

PS: I was able to work around that, by setting SHADERC_LIB_DIR = lib.makeLibraryPath [ pkgs.shaderc ];. It would still make sense to use pkg-config.