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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23888 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LowerGC.cpp

@@ -109,10 +109,11 @@ bool LowerGC::doInitialization(Module &M) {
   // If the program is using read/write barriers, find the implementations of
   // them from the GC runtime library.
   if (GCReadInt)        // Make:  sbyte* %llvm_gc_read(sbyte**)
-    GCRead = M.getOrInsertFunction("llvm_gc_read", VoidPtr, VoidPtr, VoidPtrPtr, 0);
+    GCRead = M.getOrInsertFunction("llvm_gc_read", VoidPtr, VoidPtr, VoidPtrPtr,
+                                   (Type *)0);
   if (GCWriteInt)       // Make:  void %llvm_gc_write(sbyte*, sbyte**)
     GCWrite = M.getOrInsertFunction("llvm_gc_write", Type::VoidTy,
-                                    VoidPtr, VoidPtr, VoidPtrPtr, 0);
+                                    VoidPtr, VoidPtr, VoidPtrPtr, (Type *)0);
 
   // If the program has GC roots, get or create the global root list.
   if (GCRootInt) {