[patch][pr17530] Prevent alias from pointing to weak aliases

[Reid Kleckner]

lgtm


On Thu, Mar 13, 2014 at 10:11 AM, Rafael Espíndola <
rafael.espindola at gmail.com> wrote:

> Aliases are just another name for a position in a file. As such, the
> regular symbol resolutions are not applied. For example,given
>
> define void @my_func() {
>   ret void
> }
> @my_alias = alias weak void ()* @my_func
> @my_alias2 = alias void ()* @my_alias
>
> We produce without this patch:
>
>         .weak   my_alias
> my_alias = my_func
>         .globl  my_alias2
> my_alias2 = my_alias
>
> That is, in the resulting ELF file my_alias, my_func and my_func2 are
> just 3 names pointing to offset 0 of .text. That is *not* the
> semantics of IR linking. For example, linking in a
>
> @my_alias = alias void ()* @other_func
>
> would require the strong my_alias to override the weak one and
> my_alias2 would end up pointing to other_func.
>
> There is no way to represent that with aliases being just another
> name, so the best solution seems to be to just disallow it, converting
> a miscompile into an error.
>
> Cheers,
> Rafael
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20140325/cbd587b0/attachment.html>