Description
When picking up libraries from multiple prefixes (which is quite common in practice, for example when you have /usr and /opt), it is very easy to get into a situation where the wrong library is being picked up by the linker. For example:
/prefix1/lib/libfoo.a
/prefix1/lib/libbar.a
/prefix1/lib/pkgconfig/foo.pc
/prefix1/lib/pkgconfig/bar.pc
/prefix2/lib/libfaz.a
/prefix2/lib/libbar.a
/prefix2/lib/pkgconfig/faz.pc
/prefix2/lib/pkgconfig/bar.pc
With PKG_CONFIG_PATH=/prefix1/lib/pkgconfig:/prefix2/lib/pkgconfig you'd expect libbar.a to be picked up from prefix1. But if you are aggregating flags like so:
pkg_config::probe_library("faz").unwrap();
pkg_config::probe_library("bar").unwrap();This will generate a linker line like:
[...] -L/prefix2/lib -L/prefix1/lib [...] -lfaz -lbar
The linker will resolve this to:
/prefix2/lib/libfaz.a /prefix2/lib/libbar.a
The solution is that probe_library() should resolve the -L -l flags it receives from the pc file to on-disk files immediately, and pass those files to the linker:
/prefix2/lib/libfaz.a /prefix1/lib/libbar.a
If it is unable to find the corresponding library, it can fall back to the current behaviour. This should reduce the likelihood of incorrect libs being picked up considerably.