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Re: [PATCH] BZ #5784: Build libpthread.a with ld -r
On Thu, Sep 6, 2012 at 8:30 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> 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.
>
The current design for static pthread executable is
pretty much broken and works by chance or "ld -r".
See:
http://www.sourceware.org/bugzilla/show_bug.cgi?id=14556
for 2 examples. STB_SECONDARY can be used to address
those glibc and GCC issues. I put STB_SECONDARY support
on hjl/secondary branch in glibc git and on hjl/secondary binutils
branch at
http://git.kernel.org/?p=linux/kernel/git/hjl/binutils.git;a=summary
--
H.J.