Re: [PATCH] configure: Improve alias attribute check

[Paolo Bonzini]

Il dom 21 mar 2021, 16:49 Richard Henderson <richard.henderson@linaro.org> ha scritto:

What exact version of gcc are you guys using?  Something from rawhide that I can just install?

I am using Fedora 34. I upgraded just to test this bug and it seems stable except that GNOME Shell extensions need an upgrade. However I haven't tried building all of QEMU, only the test case.

So far I have failed to compile with gcc master with --enable-lto.  Lots of
missing symbols reported at link time.  Therefore I've been unable to actually
test what I intended to test.

That said, I'm not hopeful that __attribute__((const)) will work.  I have an
idea that early inlining will inline tiny function calls too soon, before the
attribute has a change to DTRT during CSE.

Yeah that's at least plausible.

Another workaround may be to avoid compiling exec-vary.c with -flto.  I'm not
sure that my meson fu is up to that.  Paolo?

You would have to define a static library. 

I have filed a gcc bug report:

   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99696

Hopefully someone can address that before gcc 11 gets released.  At which point we need do nothing in qemu.  Aldy?

Good point, I can give it a shot too just to see how rusty I am... That would be the best outcome, though we would have to check LLVM as well. If const doesn't work it would indeed be prudent to include Gavin's configure check.

Paolo

r~