PR16074, implement warnings to catch pointer to boolean true and pointer to

null comparison when the pointer is known to be non-null.

This catches the array to pointer decay, function to pointer decay and
address of variables.  This does not catch address of function since this
has been previously used to silence a warning.

Pointer to bool conversion is under -Wbool-conversion.
Pointer to null comparison is under -Wtautological-pointer-compare, a sub-group
of -Wtautological-compare.

void foo() {
  int arr[5];
  int x;
  // warn on these conditionals
  if (foo);
  if (arr);
  if (&x);
  if (foo == null);
  if (arr == null);
  if (&x == null);

  if (&foo);  // no warning
}


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202216 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 4 deletions

diff --git a/test/SemaTemplate/resolve-single-template-id.cpp b/test/SemaTemplate/resolve-single-template-id.cpp
index 7fb16eb467..915c42c85a 100644
--- a/test/SemaTemplate/resolve-single-template-id.cpp
+++ b/test/SemaTemplate/resolve-single-template-id.cpp
@@ -45,9 +45,15 @@ int main()
   +oneT<int>;  // expected-warning {{expression result unused}}
   -oneT<int>;  //expected-error {{invalid argument type}}
   oneT<int> == 0;   // expected-warning {{equality comparison result unused}} \
-                    // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  0 == oneT<int>;   // expected-warning {{equality comparison result unused}}
-  0 != oneT<int>;    // expected-warning {{inequality comparison result unused}}
+                    // expected-note {{use '=' to turn this equality comparison into an assignment}} \
+                    // expected-warning {{comparison of function 'oneT<int>' equal to a null pointer is always false}} \
+                    // expected-note {{prefix with the address-of operator to silence this warning}}
+  0 == oneT<int>;   // expected-warning {{equality comparison result unused}} \
+                    // expected-warning {{comparison of function 'oneT<int>' equal to a null pointer is always false}} \
+                    // expected-note {{prefix with the address-of operator to silence this warning}}
+  0 != oneT<int>;   // expected-warning {{inequality comparison result unused}} \
+                    // expected-warning {{comparison of function 'oneT<int>' not equal to a null pointer is always true}} \
+                    // expected-note {{prefix with the address-of operator to silence this warning}}
   (false ? one : oneT<int>);   // expected-warning {{expression result unused}}
   void (*p1)(int); p1 = oneT<int>;
   
@@ -69,7 +75,9 @@ int main()
   two < two; //expected-error 2 {{reference to overloaded function could not be resolved; did you mean to call it with no arguments?}} expected-error {{invalid operands to binary expression ('void' and 'void')}}
   twoT<int> < twoT<int>; //expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}} {{cannot resolve overloaded function 'twoT' from context}}
   oneT<int> == 0;   // expected-warning {{equality comparison result unused}} \
-                    // expected-note {{use '=' to turn this equality comparison into an assignment}}
+                    // expected-note {{use '=' to turn this equality comparison into an assignment}} \
+                    // expected-warning {{comparison of function 'oneT<int>' equal to a null pointer is always false}} \
+                    // expected-note {{prefix with the address-of operator to silence this warning}}
 
 }