Issue a warning if a throwing operator new or operator new[] returns a null
pointer, since this invokes undefined behavior. Based on a patch by Artyom
Skrobov! Handling of dependent exception specifications and some additional
testcases by me.

llvm-svn: 199452
diff --git a/clang/test/SemaCXX/new-null.cpp b/clang/test/SemaCXX/new-null.cpp
new file mode 100644
index 0000000..b2be0c5
--- /dev/null
+++ b/clang/test/SemaCXX/new-null.cpp
@@ -0,0 +1,63 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++98
+// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++11
+
+typedef __SIZE_TYPE__ size_t;
+
+#if __cplusplus >= 201103L
+struct S1 {
+   void *operator new(size_t n) {
+     return nullptr; // expected-warning {{'operator new' should not return a null pointer unless it is declared 'throw()' or 'noexcept'}}
+   }
+   void *operator new[](size_t n) noexcept {
+     return __null;
+   }
+};
+#endif
+
+struct S2 {
+   static size_t x;
+   void *operator new(size_t n) throw() {
+     return 0;
+   }
+   void *operator new[](size_t n) {
+     return (void*)0;
+#if __cplusplus >= 201103L
+     // expected-warning@-2 {{'operator new[]' should not return a null pointer unless it is declared 'throw()' or 'noexcept'}}
+#else
+     // expected-warning-re@-4 {{'operator new[]' should not return a null pointer unless it is declared 'throw()'{{$}}}}
+#endif
+   }
+};
+
+struct S3 {
+   void *operator new(size_t n) {
+     return 1-1;
+#if __cplusplus >= 201103L
+     // expected-error@-2 {{cannot initialize return object of type 'void *' with an rvalue of type 'int'}}
+#else
+     // expected-warning@-4 {{expression which evaluates to zero treated as a null pointer constant of type 'void *'}}
+     // expected-warning@-5 {{'operator new' should not return a null pointer unless it is declared 'throw()'}}
+#endif
+   }
+   void *operator new[](size_t n) {
+     return (void*)(1-1); // expected-warning {{'operator new[]' should not return a null pointer unless it is declared 'throw()'}}
+   }
+};
+
+#if __cplusplus >= 201103L
+template<bool B> struct S4 {
+  void *operator new(size_t n) noexcept(B) {
+    return 0; // expected-warning {{'operator new' should not return a null pointer}}
+  }
+};
+template struct S4<true>;
+template struct S4<false>; // expected-note {{in instantiation of}}
+#endif
+
+template<typename ...T> struct S5 { // expected-warning 0-1{{extension}}
+  void *operator new(size_t n) throw(T...) {
+    return 0; // expected-warning {{'operator new' should not return a null pointer}}
+  }
+};
+template struct S5<>;
+template struct S5<int>; // expected-note {{in instantiation of}}