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Re: [PATCH] BZ #5784: Build libpthread.a with ld -r


On Thu, Sep 6, 2012 at 7:29 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Sep 6, 2012 at 6:25 PM, Roland McGrath <roland@hack.frob.com> wrote:
>
>>    An alternative that's more different (and off hand seems vaguely
>>    worse to me), but perhaps is better in some way or other, is to make
>>    sure that libc defines redirector functions for every pthread_foo
>>    that libstdc++ calls.  Then if -lpthread is missing, the strong
>>    references are resolved to the libc definitions, which normally do
>>    nothing.  This alternative has the advantage that, if paired with a
>>    b. solution for #1, it also correctly handles "dynamic static
>>    threadedness".
>>
>
> That is one of the intentions of STB_SECONDARY.  Libc
> can define those pthread_foo functions as STB_SECONDARY.
> If there is no -lpthread, they will be used.  Otherwise,
> those in -lpthread will be used.
>

We can simply change weak reference in GCC to
strong reference and everything should just work.
We get no extra code in static executable since
each secondary pthread_foo in libc.a is in a separate
.o file.  You only link in what you need.  We can do it
in 2 phases:

1. Implement STB_SECONDARY in glibc first.
2. Use strong reference in GCC if glibc has
secondary pthread_foo.

-- 
H.J.


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