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Re: PATCH: Add ifunc attribute


On Sat, Jun 13, 2009 at 6:07 PM, H.J. Lu<hjl.tools@gmail.com> wrote:
> On Sat, Jun 13, 2009 at 8:15 AM, Richard
> Guenther<richard.guenther@gmail.com> wrote:
>
>>>
>>> I started to write my own version of the documentation, but I realized
>>> that I don't even understand this. ?Which function is called by the
>>> dynamic linker, "f" or "f_ifunc"? ?Why is the attribute ignored if
>>> "f_ifunc" is not defined; shouldn't it be an error? ?I guess that means
>>> that "f_ifunc" is called by the dynamic linker; in that case, what
>>> happens if "func" is defined?
>>
>> Yeah. ?I would have proposed that
>>
>> void *foo (void) __attribute__((__ifunc__))
>> {
>> ?return zero;
>> }
>>
>> would simply generate foo with indirect function type.
>>
>> This of course causes a problem if you have a declaration for
>> the real foo available - but then you should better not have that,
>> as the compiler will then derive wrong properties for the real foo
>> from the ifunc wrapper body.
>>
>
> Glibc has ifunc testcases with a declaration of foo in the same file.
> This proposal won't work with them.

They would just need to be fixed then.

Richard.


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