[LLVMdev] Weak private linkage for Objective C

[Harel Cain]

I'm just trying to raise this problem again as I got no answer at all.
Nobody has any information about support or workarounds for weak private
linkage for Mach-O objects? See below.

Thanks!

Harel Cain

On Sun, Dec 5, 2010 at 3:54 PM, Harel Cain <harel.cain at gmail.com> wrote:

> Hi all,
>
> I've been subscribed to this list on-and-off and always found it very
> helpful.
>
> I'm facing the problem of compiling a project in Objective C with LLVM in a
> Darwin environment. There is a certain Objective C protocol that appears in
> two .m files, and so the corresponding l_OBJC_PROTOCOL and
> l_OBJC_LABEL_PROTOCOL symbols appear in both .o files.
>
> The problem is that while these symbols are created by gcc 4.2 as *weak*
> private external, LLVM (both 2.8 and bleeding-edge) produces these symbols
> as private external, but not weak. Because they are not weak, the linker
> (ld) shouts at the duplicate symbol. If I semi-manually patch the Mach-O
> object files to make these symbols weak [following this documentation:
> http://developer.apple.com/library/mac/documentation/DeveloperTools/Conceptual/MachORuntime/Reference/reference.html#//apple_ref/doc/uid/20001298-section],
> then the problem is solved.
>
> I saw a thread here from June 2010 (
> http://lists.cs.uiuc.edu/pipermail/llvmdev/2010-June/032767.html) about
> the weak private linkage type, but I'm not sure it's now merged into the
> trunk (it seems to me it's not) or how to use it exactly.
>
> Is there some command-line flag I can give llvm-gcc or llvmc to make the
> Objective C protocols appear as weak private symbols in the object files?
> Any other way to work around this problem of mine?
>
>
> Many thanks in advance,
>
> Harel Cain
>
>
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