rustc --test -l static=somelib.a links with --whole-archive

[xclaesse]

Originally reported as #116900, but the actual bug affects every libraries and platforms.

rustc --test -l static:+verbatim=libsomelib.a generates the linker command -Wl,--whole-archive -l:libsomelib.a -Wl,--no-whole-archive. Without --test it correctly doesn't link whole archive.

It is expected to link whole archive only if passing +whole-archive modifier.

[Noratrieb]

@petrochenkov @lqd @bjorn3 or whoever wants to look at linkage troubles today

[bjorn3]

Looks like it is a back compat hack:

rust/compiler/rustc_codegen_ssa/src/back/link.rs

Lines 2471 to 2478 in a01382d

	// Backward compatibility case: this can be a rlib (so `+whole-archive`
	// cannot be added explicitly if necessary, see the error in `fn link_rlib`)
	// compiled as an executable due to `--test`. Use whole-archive implicitly,
	// like before the introduction of native lib modifiers.
	|| (whole_archive == None
	&& bundle
	&& cnum == LOCAL_CRATE
	&& sess.is_test_crate());

[xclaesse]

Not sure to understand why tests are special, but it's intentional from #95606 indeed. Feels like a bad workaround for missing +whole-archive modifiers in some projects?

[bjorn3]

My reading from the code comment is that you can't aren't allowed to use +whole-archive for tests of rlib crates at all, not that some projects are missing it.

[xclaesse]

you aren't allowed to use +whole-archive for tests of rlib crates at all

Why is that not allowed? That would be the root issue then?

[bjorn3]

It seems like +bundle and +whole-archive are not compatible with each other for rlibs. Someone else may know better why this is the case. It's been a while since I last looked at this code.

[petrochenkov]

The +bundle,+whole-archive combination was recently stabilized in #113301 so it may be possible to remove this hack now.
We'll just need to run crater, send fixes to affected crates, and all that stuff.

[petrochenkov]

Fixed in #128400.