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From: Rich Felker <dalias@libc.org>
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Subject: Re: building musl libc.so with gcc -flto
Date: Tue, 28 Apr 2015 09:44:53 -0400
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On Mon, Apr 27, 2015 at 11:23:40PM -0700, Andre McCurdy wrote:
> On Mon, Apr 27, 2015 at 5:24 PM, Rich Felker <dalias@libc.org> wrote:
> > On Mon, Apr 27, 2015 at 05:16:12PM -0700, Andre McCurdy wrote:
> >> > OK, it looks like the _dlstart_c symbol got removed before linking the
> >> > asm. What about selectively compiling this file with -fno-lto via
> >> > something like this in config.mak:
> >> >
> >> > src/ldso/dlstart.lo: CFLAGS += -fno-lto
> >>
> >> That works. Should I send a patch?
> >
> > Yes, but configure would need to detect support for -fno-lto and add
> > it appropriately. See what's done for CFLAGS_NOSSP. I suspect the crt
> > files also need -fno-lto in principle even if they're not currently
> > breaking for lack of it.
> 
> Patch sent.
> 
> I think the crt files might be OK as they are, since the _start_c
> symbol isn't being hidden?

I think you'll find the exact same thing happens if you use a crt1.o
produced from crt1.c for static linking with LTO. Note that on i386
(and x86_64) we still have a crt1.s which overrides crt1.c; I want to
remove it at some point. Temporarily removing/renaming it yourself
will allow you to test what happens with LTO on this file.

Rich