[PATCH v2] Improve building with LTO

[Mark Wielaard]

Hi Dmitry,

On Mon, Nov 08, 2021 at 01:02:28PM +0300, Dmitry V. Levin wrote:
> > Thanks. This patch was indeed one reason I kept postponing the release,
> > because I didn't have have time to properly review it.
> > 
> > Which gcc versions have you tried this against (with/without -flto?)
> 
> I tested with gcc10 and gcc11.
> I could try older versions, although I didn't feel that necessary.

I also did try with gcc 4.8 and gcc 8 (both without lto though).

> https://sourceware.org/bugzilla/show_bug.cgi?id=27367 will likely strike
> those who would build elfutils with -flto using gcc11+.

But only if they use -ffat-lto-objects (which isn't the default)?  Did
you see and try the patch I proposed? Do you think we should include
it? I would like someone else to check/try it.

> > does also impact symbol versioning for non-lto builds, so I am still a
> > little hesitant. I'll try to do some tests to make sure things look ok
> > with different gcc versions.
> 
> What do you mean by "it does also impact symbol versioning for non-lto
> builds"?  The code for non-lto builds changes, but the versioning
> should remain the same, shouldn't it?

I meant I am paranoid :) We are using slightly different asm or an
attribute to mark the symbol version than we did before. But I double
checked the exported versioned symbols with and without this patch on
different gcc versions and they look fine.

So I did just now push this patch.

Cheers,

Mark