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[committed, PATCH] x86: Properly check building shared library

H.J. Lu hjl.tools@gmail.com
Wed Feb 14 05:13:00 GMT 2018 
On Tue, Feb 13, 2018 at 6:11 PM, Alan Modra <amodra@gmail.com> wrote:
> On Tue, Feb 13, 2018 at 02:31:43PM -0800, H.J. Lu wrote:
>> If a symbol is not defined in a regular file, and we are not generating
>> a shared library, then set the symbol to its location in the .plt.  This
>> is required to make function pointers compare as equal between the normal
>> executable and the shared library.
>
> I'm curious as to why this is necessary, in case other targets need
> the same treatment.  Normally a PIE is built from position independent
> code, and thus addresses of functions are loaded from the GOT.  That
> means there is no need to use any tricks to avoid dynamic text relocs.
>

This is true in most cases.  However, you can use PC-relative relocation
to compute function address without GOT.  Here is a patch for

https://sourceware.org/bugzilla/show_bug.cgi?id=22842

with testcases in assembly for i386 and x86-64.  I think you can create
similar testcases for other targets.

I will check it in tomorrow.

-- 
H.J.
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