When a function takes a variable number of pointer arguments, with a zero

pointer marking the end of the list, the zero *must* be cast to the pointer
type.  An un-cast zero is a 32-bit int, and at least on x86_64, gcc will
not extend the zero to 64 bits, thus allowing the upper 32 bits to be
random junk.

The new END_WITH_NULL macro may be used to annotate a such a function
so that GCC (version 4 or newer) will detect the use of un-casted zero
at compile time.

llvm-svn: 23888

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/IntrinsicLowering.cpp b/llvm/lib/CodeGen/IntrinsicLowering.cpp
index b2dd57b50c2..a570ef54c45 100644
--- a/llvm/lib/CodeGen/IntrinsicLowering.cpp
+++ b/llvm/lib/CodeGen/IntrinsicLowering.cpp
@@ -110,7 +110,8 @@ void DefaultIntrinsicLowering::AddPrototypes(Module &M) {
       case Intrinsic::memset:
         M.getOrInsertFunction("memset", PointerType::get(Type::SByteTy),
                               PointerType::get(Type::SByteTy),
-                              Type::IntTy, (--(--I->arg_end()))->getType(), 0);
+                              Type::IntTy, (--(--I->arg_end()))->getType(),
+                              (Type *)0);
         break;
       case Intrinsic::isunordered:
         EnsureFunctionExists(M, "isunordered", I->arg_begin(), I->arg_end(),