From f165cf7ce8d8df9b136604b1542dd9b4980793fe Mon Sep 17 00:00:00 2001 From: Rafael Espindola Date: Thu, 27 Mar 2014 15:26:56 +0000 Subject: Prevent alias from pointing to weak aliases. This adds back r204781. Original message: 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_alias 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204934 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/LangRef.rst | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'docs/LangRef.rst') diff --git a/docs/LangRef.rst b/docs/LangRef.rst index adf3266b02..91692ad41e 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -681,6 +681,10 @@ the aliasee. The aliasee must be a definition. +Aliases are not allowed to point to aliases with linkages that can be +overridden. Since they are only a second name, the possibility of the +intermediate alias being overridden cannot be represented in an object file. + .. _namedmetadatastructure: Named Metadata -- cgit v1.2.3