remove -L/ and -l: from linker flags

[spitulax]

This is the actual fix to NixOS/nixpkgs#338972 and many other issues with linking on Nix build system. The issue may have been caused by using -l: to specify the path to libraries and -L/ to set the linker search path. The linker could not find the libraries only when building using Nix stdenv. Building inside a nix shell does not trigger this issue. Probably it has something to do with build sandboxing, but I'm not too knowledgeable on this matter.

I found the solution when I was trying to isolate the issue using a simple C program and a static library. Building this with nix stdenv, resulting in the linker not being able to found the library.

buildPhase = ''
    gcc -o main main.c -L/ -l:$(pwd)/lib/libh.a
'';

/nix/store/j7p46r8v9gcpbxx89pbqlh61zhd33gzv-binutils-2.43.1/bin/ld: cannot find -l:/build/source/lib/libh.a: No such file or directory

But removing -L/ and -l: does the trick.

buildPhase = ''
    gcc -o main main.c $(pwd)/lib/libh.a
'';

I also tested this patch on Debian and it seemed to work fine.

[gingerBill]

Wouldn't it better to disable them just for Nix?

[flysand7]

@gingerBill There are some differences between specifying -l: and -L and not doing that, but yes, these should be disabled just for Nix, if we want to disable them.

I also believe that we need to update the way these flags are handled in the presence of

• foreign import "lib"; and
• foreign import "system:lib"

Since system: explicitly asks for it to be a system dependency. Currently system: directive is only used to special-case some common libraries -- libc, m and thread, which I think needs to be fixed in the future at some point.