Downgrade errors when trying to catch a pointer or reference to

incomplete type to warnings; GCC (and EDG in GCC compatibility mode)
permit such handles. Fixes PR6527.

(For real this time)


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97927 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -2048,10 +2048,10 @@ def note_delete_member_function_declared_here : Note<
 def err_decrement_bool : Error<"cannot decrement expression of type bool">;
 def warn_increment_bool : Warning<
   "incrementing expression of type bool is deprecated">, InGroup<Deprecated>;
-def err_catch_incomplete_ptr : Error<
-  "cannot catch pointer to incomplete type %0">;
-def err_catch_incomplete_ref : Error<
-  "cannot catch reference to incomplete type %0">;
+def ext_catch_incomplete_ptr : ExtWarn<
+  "ISO C++ forbids catching a pointer to incomplete type %0">;
+def ext_catch_incomplete_ref : ExtWarn<
+  "ISO C++ forbids catching a 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_qualified_catch_declarator : Error<

lib/Sema/SemaDeclCXX.cpp

@@ -5195,21 +5195,28 @@ VarDecl *Sema::BuildExceptionDeclaration(Scope *S, QualType ExDeclType,
     Invalid = true;
   }
 
+  // GCC allows catching pointers and references to incomplete types
+  // as an extension; so do we, but we warn by default.
+
   QualType BaseType = ExDeclType;
   int Mode = 0; // 0 for direct type, 1 for pointer, 2 for reference
   unsigned DK = diag::err_catch_incomplete;
+  bool IncompleteCatchIsInvalid = true;
   if (const PointerType *Ptr = BaseType->getAs<PointerType>()) {
     BaseType = Ptr->getPointeeType();
     Mode = 1;
-    DK = diag::err_catch_incomplete_ptr;
+    DK = diag::ext_catch_incomplete_ptr;
+    IncompleteCatchIsInvalid = false;
   } else if (const ReferenceType *Ref = BaseType->getAs<ReferenceType>()) {
     // For the purpose of error recovery, we treat rvalue refs like lvalue refs.
     BaseType = Ref->getPointeeType();
     Mode = 2;
-    DK = diag::err_catch_incomplete_ref;
+    DK = diag::ext_catch_incomplete_ref;
+    IncompleteCatchIsInvalid = false;
   }
   if (!Invalid && (Mode == 0 || !BaseType->isVoidType()) &&
-      !BaseType->isDependentType() && RequireCompleteType(Loc, BaseType, DK))
+      !BaseType->isDependentType() && RequireCompleteType(Loc, BaseType, DK) &&
+      IncompleteCatchIsInvalid)
     Invalid = true;
 
   if (!Invalid && !ExDeclType->isDependentType() &&

test/SemaCXX/exceptions.cpp

@@ -12,8 +12,8 @@ void trys() {
   } catch(float i) {
   } catch(void v) { // expected-error {{cannot catch incomplete type 'void'}}
   } catch(A a) { // expected-error {{cannot catch incomplete type 'struct A'}}
-  } catch(A *a) { // expected-error {{cannot catch pointer to incomplete type 'struct A'}}
-  } catch(A &a) { // expected-error {{cannot catch reference to incomplete type 'struct A'}}
+  } catch(A *a) { // expected-warning {{pointer to incomplete type 'struct A'}}
+  } catch(A &a) { // expected-warning {{reference to incomplete type 'struct A'}}
   } catch(Abstract) { // expected-error {{variable type 'Abstract' is an abstract class}}
   } catch(...) {
     int j = i; // expected-error {{use of undeclared identifier 'i'}}

test/SemaTemplate/instantiate-function-1.cpp

@@ -194,7 +194,7 @@ template struct IndirectGoto0<int>; // expected-note{{instantiation}}
 template<typename T> struct TryCatch0 {
   void f() {
     try {
-    } catch (T t) { // expected-error{{incomplete type}} \
+    } catch (T t) { // expected-warning{{incomplete type}} \
                     // expected-error{{abstract class}}
     } catch (...) {
     }