Implement warning for integral null pointer constants other than the literal 0.

This is effectively a warning for code that violates core issue 903 & thus will
become standard error in the future, hopefully. It catches strange null
pointers such as: '\0', 1 - 1, const int null = 0; etc...

There's currently a flaw in this warning (& the warning for 'false' as a null
pointer literal as well) where it doesn't trigger on comparisons (ptr == '\0'
for example). Fix to come in a future patch.

Also, due to this only being a warning, not an error, it triggers quite
frequently on gtest code which tests expressions for null-pointer-ness in a
SFINAE context (so it wouldn't be a problem if this was an error as in an
actual implementation of core issue 903). To workaround this for now, the
diagnostic does not fire in unevaluated contexts.

Review by Sean Silva and Richard Smith.

llvm-svn: 161501

1 files changed, 3 insertions, 3 deletions

diff --git a/clang/test/SemaCXX/lambda-expressions.cpp b/clang/test/SemaCXX/lambda-expressions.cpp
index 198f8cf1fef..0fd634502bc 100644
--- a/clang/test/SemaCXX/lambda-expressions.cpp
+++ b/clang/test/SemaCXX/lambda-expressions.cpp
@@ -117,16 +117,16 @@ namespace NullPtr {
 
     const int m = 0;
     [=] {
-      int &k = f(m); // a null pointer constant
+      int &k = f(m); // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
     } ();
 
     [=] () -> bool {
-      int &k = f(m); // a null pointer constant
+      int &k = f(m); // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
       return &m == 0;
     } ();
 
     [m] {
-      int &k = f(m); // a null pointer constant
+      int &k = f(m); // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
     } ();
   }
 }