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

Rafael EspĂ­ndola rafael.espindola at gmail.com
Thu Mar 13 10:11:50 PDT 2014

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.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: t.patch
Type: text/x-patch
Size: 14844 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20140313/858f2b7a/attachment.bin>

More information about the llvm-commits mailing list