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

3 files changed, 11 insertions, 2 deletions

diff --git a/include/llvm/Module.h b/include/llvm/Module.h
index d4932fc855..d491c752fd 100644
--- a/include/llvm/Module.h
+++ b/include/llvm/Module.h
@@ -22,6 +22,7 @@
 #include "llvm/Function.h"
 #include "llvm/GlobalVariable.h"
 #include "llvm/ADT/SetVector.h"
+#include "llvm/Support/DataTypes.h"
 
 namespace llvm {
 
@@ -111,7 +112,8 @@ public:
   /// table.  If it does not exist, add a prototype for the function and return
   /// it.  This version of the method takes a null terminated list of function
   /// arguments, which makes it easier for clients to use.
-  Function *getOrInsertFunction(const std::string &Name, const Type *RetTy,...);
+  Function *getOrInsertFunction(const std::string &Name, const Type *RetTy,...)
+    END_WITH_NULL;
 
   /// getFunction - Look up the specified function in the module symbol table.
   /// If it does not exist, return null.
diff --git a/include/llvm/Support/CommandLine.h b/include/llvm/Support/CommandLine.h
index 10a2f6c6ab..1d499de9a9 100644
--- a/include/llvm/Support/CommandLine.h
+++ b/include/llvm/Support/CommandLine.h
@@ -21,6 +21,7 @@
 #define LLVM_SUPPORT_COMMANDLINE_H
 
 #include "llvm/Support/type_traits.h"
+#include "llvm/Support/DataTypes.h"
 #include <string>
 #include <vector>
 #include <utility>
@@ -335,7 +336,7 @@ public:
 
 template<class DataType>
 ValuesClass<DataType> values(const char *Arg, DataType Val, const char *Desc,
-                             ...) {
+                             ...) END_WITH_NULL {
     va_list ValueArgs;
     va_start(ValueArgs, Desc);
     ValuesClass<DataType> Vals(Arg, Val, Desc, ValueArgs);
diff --git a/include/llvm/Support/DataTypes.h.in b/include/llvm/Support/DataTypes.h.in
index b99739dc4e..cfec5f3862 100644
--- a/include/llvm/Support/DataTypes.h.in
+++ b/include/llvm/Support/DataTypes.h.in
@@ -98,4 +98,10 @@ typedef signed int ssize_t;
 # define UINT64_MAX 0xffffffffffffffffULL
 #endif
 
+#if __GNUC__ > 3
+#define END_WITH_NULL __attribute__((sentinel))
+#else
+#define END_WITH_NULL
+#endif
+
 #endif  /* SUPPORT_DATATYPES_H */