Introduce Wzero-as-null-pointer-constant.

Add an opt-in warning that fires when 0 is used as a null pointer. 
gcc has this warning, and there's some demand for it.

https://reviews.llvm.org/D32914

llvm-svn: 302247

1 files changed, 27 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/warn-zero-nullptr.cpp b/clang/test/SemaCXX/warn-zero-nullptr.cpp
new file mode 100644
index 00000000000..edd2a759b70
--- /dev/null
+++ b/clang/test/SemaCXX/warn-zero-nullptr.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -Wzero-as-null-pointer-constant -std=c++11
+
+struct S {};
+
+int (S::*mp0) = nullptr;
+void (*fp0)() = nullptr;
+void* p0 = nullptr;
+
+int (S::*mp1) = 0; // expected-warning{{zero as null pointer constant}}
+void (*fp1)() = 0; // expected-warning{{zero as null pointer constant}}
+void* p1 = 0; // expected-warning{{zero as null pointer constant}}
+
+// NULL is an integer constant expression, so warn on it too:
+void* p2 = __null; // expected-warning{{zero as null pointer constant}}
+void (*fp2)() = __null; // expected-warning{{zero as null pointer constant}}
+int (S::*mp2) = __null; // expected-warning{{zero as null pointer constant}}
+
+void f0(void* v = 0); // expected-warning{{zero as null pointer constant}}
+void f1(void* v);
+
+void g() {
+  f1(0); // expected-warning{{zero as null pointer constant}}
+}
+
+// Warn on these too. Matches gcc and arguably makes sense.
+void* pp = (decltype(nullptr))0; // expected-warning{{zero as null pointer constant}}
+void* pp2 = static_cast<decltype(nullptr)>(0); // expected-warning{{zero as null pointer constant}}