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[PATCH] PR ld/19636: [x86] Resolve undefweak and defined symbols in executable

Alan Modra amodra@gmail.com
Wed Feb 24 01:39:00 GMT 2016 
On Tue, Feb 23, 2016 at 09:58:14AM -0800, H.J. Lu wrote:
> For i386 and x86-64, undefined weak and defined symbols are resolved
> without dynamic relocation when creating executable.  Undefined weak
> symbols aren't needed in the dynamic symbol table in executable.  One
> exception is on i386, we need undefined weak symbols in the dynamic
> symbol table in PIE if input relocatable files contain branchs without
> PLT so that we can branch to 0 with dynamic relocation in text section.
> 
> This makes behaviors of static excutable, dynamic excutable and position
> independent executable consistent with references to undefined weak and
> defined symbols, regardless if the relocatable input is compiled with
> PIC or not.

People know that PIC and non-PIC are different on x86 and many other
architectures.  For example, a quick google search turns up
https://glandium.org/blog/?p=2764

"On Linux systems, this just works. Compile the program (you’ll need
to build it with -fPIC, though)..."

I've seen other references to this feature, which you will break with
your patch.  Quite frankly, if this is new to you, as you say in
https://sourceware.org/ml/binutils/2016-02/msg00290.html then you
should not be rushing so quickly into this change.

-- 
Alan Modra
Australia Development Lab, IBM
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