Regression: crt* Objects not found in library search path after #158823

[farao]

I faced a regression in building rust for l4re introduced by #158823. The core of the problem seems to be that FileSearch (from compilter/rustc_session/src/filesearch.rs) is used both to locate C runtime objects (crt*) and native libraries. However, #158823 introduces a prefix-filtering of the files found in the search paths (given by "-L" or "-Lnative") and this prefix only selects libraries and discards crt objects:

let prefixes = ["lib", &target.staticlib_prefix, &target.dll_prefix];
...
    if !prefixes.iter().any(|prefix| filename.starts_with(prefix)) {                                                                                                          
      return None;                                                                                                                                                          
    }                                                                                                                                                                         

A bit more detailled: My target config uses pre_link_objects to define the file names of the crt* files. These files are searched for in rustc_codegen_ssa/src/back/link.rs in link_natively(...) via get_object_file_path(..) which after the change uses get_file_candidates(...) which due to the filtering explained above only includes libraries.

[lqd]

cc @Kobzol

[Kobzol]

Bah, I knew that I should skip this micro-optimization and only use get_file_candidates for the rlib lookup. Thanks for the report! #160449 should hopefully fix this.