Fix for llvm.org/PR23161

[eszasip]

Summary

The misc-static-assert check will not warn on the followings:

• assert(NULL == "shouldn't warn");
• assert(__null == "shouldn't warn");

Where NULL is a macro defined as __null.

[alexfh]

Awesome! Thanks!

LG

[eszasip]

Committed: r236812.

clang-tidy/misc/StaticAssertCheck.cpp

 void StaticAssertCheck::registerMatchers(MatchFinder *Finder) {
   auto IsAlwaysFalse = expr(ignoringParenImpCasts(
       expr(anyOf(boolLiteral(equals(false)), integerLiteral(equals(0)),
-          nullPtrLiteralExpr())).bind("isAlwaysFalse")));
+          nullPtrLiteralExpr(), gnuNullExpr())).bind("isAlwaysFalse")));
   auto IsAlwaysFalseWithCast = ignoringParenImpCasts(anyOf(IsAlwaysFalse,
       cStyleCastExpr(has(IsAlwaysFalse)).bind("castExpr")));
   auto AssertExprRoot = anyOf(

test/clang-tidy/misc-static-assert.cpp

   assert(NULL && "Report me!");
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be
   // CHECK-FIXES: {{^  }}static_assert(NULL , "Report me!");
+
+#define NULL __null
+  assert(__null == "Don't report me!");
+  // CHECK-FIXES: {{^  }}assert(__null == "Don't report me!");
+  assert(NULL == "Don't report me!");
+  // CHECK-FIXES: {{^  }}assert(NULL == "Don't report me!");
 #undef NULL
 
   assert(ZERO_MACRO && "Report me!");