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 --- include/llvm/IR/GlobalAlias.h | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) (limited to 'include/llvm/IR') diff --git a/include/llvm/IR/GlobalAlias.h b/include/llvm/IR/GlobalAlias.h index 81777af386..2ca481a515 100644 --- a/include/llvm/IR/GlobalAlias.h +++ b/include/llvm/IR/GlobalAlias.h @@ -64,23 +64,15 @@ public: Constant *getAliasee() { return getOperand(0); } - /// getAliasedGlobal() - Aliasee can be either global or bitcast of - /// global. This method retrives the global for both aliasee flavours. + + /// This method tries to ultimately resolve the alias by going through the + /// aliasing chain and trying to find the very last global. Returns NULL if a + /// cycle was found. GlobalValue *getAliasedGlobal(); const GlobalValue *getAliasedGlobal() const { return const_cast(this)->getAliasedGlobal(); } - /// resolveAliasedGlobal() - This method tries to ultimately resolve the alias - /// by going through the aliasing chain and trying to find the very last - /// global. Returns NULL if a cycle was found. If stopOnWeak is false, then - /// the whole chain aliasing chain is traversed, otherwise - only strong - /// aliases. - GlobalValue *resolveAliasedGlobal(bool stopOnWeak = true); - const GlobalValue *resolveAliasedGlobal(bool stopOnWeak = true) const { - return const_cast(this)->resolveAliasedGlobal(stopOnWeak); - } - static bool isValidLinkage(LinkageTypes L) { return isExternalLinkage(L) || isLocalLinkage(L) || isWeakLinkage(L) || isLinkOnceLinkage(L); -- cgit v1.2.3