Teach EvaluatedExprVisitor that the condition and unselected branches of a

_Generic expression are unevaluated.

llvm-svn: 223266

clang/include/clang/AST/EvaluatedExprVisitor.h

@@ -56,6 +56,17 @@ public:
     return this->Visit(E->getChosenSubExpr());
   }
 
+  void VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    // The controlling expression of a generic selection is not evaluated.
+
+    // Don't visit either child expression if the condition is type-dependent.
+    if (E->isResultDependent())
+      return;
+    // Only the selected subexpression matters; the other subexpressions and the
+    // controlling expression are not evaluated.
+    return this->Visit(E->getResultExpr());
+  }
+
   void VisitDesignatedInitExpr(DesignatedInitExpr *E) {
     // Only the actual initializer matters; the designators are all constant
     // expressions.

clang/test/Sema/warn-unsequenced.c

@@ -90,4 +90,7 @@ void test() {
   (__builtin_classify_type(++a) ? 1 : 0) + ++a; // ok
   (__builtin_constant_p(++a) ? 1 : 0) + ++a; // ok
   (__builtin_expect(++a, 0) ? 1 : 0) + ++a; // expected-warning {{multiple unsequenced modifications}}
+  _Generic(++a, default: 0) + ++a; // ok
+  sizeof(++a) + ++a; // ok
+  _Alignof(++a) + ++a; // expected-warning {{extension}}
 }