[Sema] Don't permit catching variably modified types

Variably modified types shouldn't be permitted in catch clauses.

This fixes PR28047.

llvm-svn: 272159

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -5904,6 +5904,8 @@ def err_catch_incomplete_ref : Error<
   "cannot catch reference to incomplete type %0">;
 def err_catch_incomplete : Error<"cannot catch incomplete type %0">;
 def err_catch_rvalue_ref : Error<"cannot catch exceptions by rvalue reference">;
+def err_catch_variably_modified : Error<
+  "cannot catch variably modified type %0">;
 def err_qualified_catch_declarator : Error<
   "exception declarator cannot be qualified">;
 def err_early_catch_all : Error<"catch-all handler must come last">;

clang/lib/Sema/SemaDeclCXX.cpp

@@ -12207,6 +12207,11 @@ VarDecl *Sema::BuildExceptionDeclaration(Scope *S,
     Invalid = true;
   }
 
+  if (ExDeclType->isVariablyModifiedType()) {
+    Diag(Loc, diag::err_catch_variably_modified) << ExDeclType;
+    Invalid = true;
+  }
+
   QualType BaseType = ExDeclType;
   int Mode = 0; // 0 for direct type, 1 for pointer, 2 for reference
   unsigned DK = diag::err_catch_incomplete;

clang/test/SemaCXX/exceptions.cpp

@@ -268,3 +268,17 @@ void g() {
   }
 }
 }
+
+namespace PR28047 {
+void test1(int i) {
+  try {
+  } catch (int(*)[i]) { // expected-error{{cannot catch variably modified type}}
+  }
+}
+void test2() {
+  int i;
+  try {
+  } catch (int(*)[i]) { // expected-error{{cannot catch variably modified type}}
+  }
+}
+}