Patchwork [C++] PR 57599

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Submitter Paolo Carlini
Date June 13, 2013, 12:49 a.m.
Message ID <51B91718.2010900@oracle.com>
Download mbox | patch
Permalink /patch/250941/
State New
Headers show

Comments

Paolo Carlini - June 13, 2013, 12:49 a.m.
Hi,

this dynamic_cast bug, which just came in, notices that in the simple 
case of static conversion we forget to perform the cv-qualifier 
conversions. It seems to me that we are missing a build_nop.

I extended quite a bit the testcase, to references too, because at some 
point I got those wrong ;)

Tested x86_64-linux.

Thanks,
Paolo.

//////////////////////////
/cp
2013-06-13  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/57599
	* rtti.c (build_dynamic_cast_1): In case of static conversion,
	remember to perform the cv-qualifier conversions.

/testsuite
2013-06-13  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/57599
	* g++.dg/rtti/dyncast6.C: New.
Jason Merrill - June 13, 2013, 1:51 p.m.
On 06/12/2013 08:49 PM, Paolo Carlini wrote:
> +	/* Add any qualifier conversions.  */
> +	return build_nop (type, expr);

For a cast to reference type, this will produce an rvalue rather than an 
lvalue.

Perhaps we should hand off to build_static_cast in the case described by 
the comment, rather than duplicate the logic.

Jason
Paolo Carlini - June 13, 2013, 2:03 p.m.
Hi,

Jason Merrill <jason@redhat.com> ha scritto:

>On 06/12/2013 08:49 PM, Paolo Carlini wrote:
>> +	/* Add any qualifier conversions.  */
>> +	return build_nop (type, expr);
>
>For a cast to reference type, this will produce an rvalue rather than
>an lvalue.

Ah, thanks a lot for the clarification. Admittedly, I still find the whole area of nops rather obscure.

>Perhaps we should hand off to build_static_cast in the case described
>by
>the comment, rather than duplicate the logic.

Thanks for hint, I'll try to come up with another try over the next day or so.

Thanks again,
Paolo

Patch

Index: cp/rtti.c
===================================================================
--- cp/rtti.c	(revision 200041)
+++ cp/rtti.c	(working copy)
@@ -633,7 +633,8 @@  build_dynamic_cast_1 (tree type, tree expr, tsubst
 				binfo, 0, complain);
 	if (TYPE_PTR_P (exprtype))
 	  expr = rvalue (expr);
-	return expr;
+	/* Add any qualifier conversions.  */
+	return build_nop (type, expr);
       }
   }
 
Index: testsuite/g++.dg/rtti/dyncast6.C
===================================================================
--- testsuite/g++.dg/rtti/dyncast6.C	(revision 0)
+++ testsuite/g++.dg/rtti/dyncast6.C	(working copy)
@@ -0,0 +1,59 @@ 
+// PR c++/57599
+
+class A { };
+
+class B : public A { };
+
+void p()
+{
+  B* b;
+
+  A* a1;
+  a1 = dynamic_cast<A*>(b);
+  a1 = dynamic_cast<const A*>(b);          // { dg-error "invalid" }
+  a1 = dynamic_cast<volatile A*>(b);       // { dg-error "invalid" }
+  a1 = dynamic_cast<const volatile A*>(b); // { dg-error "invalid" }
+
+  const A* a2;
+  a2 = dynamic_cast<A*>(b);
+  a2 = dynamic_cast<const A*>(b);
+  a2 = dynamic_cast<volatile A*>(b);       // { dg-error "invalid" }
+  a2 = dynamic_cast<const volatile A*>(b); // { dg-error "invalid" }
+
+  volatile A* a3;
+  a3 = dynamic_cast<A*>(b);
+  a3 = dynamic_cast<const A*>(b);          // { dg-error "invalid" }
+  a3 = dynamic_cast<volatile A*>(b);
+  a3 = dynamic_cast<const volatile A*>(b); // { dg-error "invalid" }
+
+  const volatile A* a4;
+  a4 = dynamic_cast<A*>(b);
+  a4 = dynamic_cast<const A*>(b);
+  a4 = dynamic_cast<volatile A*>(b);
+  a4 = dynamic_cast<const volatile A*>(b);
+}
+
+void r()
+{
+  B b;
+
+  A& a1 = dynamic_cast<A&>(b);
+  A& a2 = dynamic_cast<const A&>(b);                // { dg-error "invalid" }
+  A& a3 = dynamic_cast<volatile A&>(b);             // { dg-error "invalid" }
+  A& a4 = dynamic_cast<const volatile A&>(b);       // { dg-error "invalid" }
+
+  const A& ca1 = dynamic_cast<A&>(b);
+  const A& ca2 = dynamic_cast<const A&>(b);
+  const A& ca3 = dynamic_cast<volatile A&>(b);       // { dg-error "invalid" }
+  const A& ca4 = dynamic_cast<const volatile A&>(b); // { dg-error "invalid" }
+
+  volatile A& va1 = dynamic_cast<A&>(b);
+  volatile A& va2 = dynamic_cast<const A&>(b);       // { dg-error "invalid" }
+  volatile A& va3 = dynamic_cast<volatile A&>(b);
+  volatile A& va4 = dynamic_cast<const volatile A&>(b);// { dg-error "invalid" }
+
+  const volatile A& cva1 = dynamic_cast<A&>(b);
+  const volatile A& cva2 = dynamic_cast<const A&>(b);
+  const volatile A& cva3 = dynamic_cast<volatile A&>(b);
+  const volatile A& cva4 = dynamic_cast<const volatile A&>(b);
+}