C++ PATCH for c++/85033, ICE with enumerator in __builtin_offsetof

Message ID 20180323104802.GM3522@redhat.com
State New
Headers show
Series
  • C++ PATCH for c++/85033, ICE with enumerator in __builtin_offsetof
Related show

Commit Message

Marek Polacek March 23, 2018, 10:48 a.m.
In this test:

struct S {
    enum { X };
};

int
foo (struct S s)
{
  return s.X;
}

unlike in C, lookup_member in C++ is able to find X in S.  So in the following
testcase finish_offsetof happily passes the CONST_DECL X down to fold_offsetof,
which then crashes because fold_offsetof_1 doesn't handle CONST_DECLs.  I think
let's simply disallow 'em in finish_offsetof; we can't take their address anyway.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2018-03-23  Marek Polacek  <polacek@redhat.com>

	PR c++/85033
	* semantics.c (finish_offsetof): Don't allow CONST_DECLs.

	* g++.dg/ext/builtin-offsetof2.C: New test.


	Marek

Comments

Jason Merrill March 23, 2018, 12:35 p.m. | #1
OK.

On Fri, Mar 23, 2018 at 6:48 AM, Marek Polacek <polacek@redhat.com> wrote:
> In this test:

>

> struct S {

>     enum { X };

> };

>

> int

> foo (struct S s)

> {

>   return s.X;

> }

>

> unlike in C, lookup_member in C++ is able to find X in S.  So in the following

> testcase finish_offsetof happily passes the CONST_DECL X down to fold_offsetof,

> which then crashes because fold_offsetof_1 doesn't handle CONST_DECLs.  I think

> let's simply disallow 'em in finish_offsetof; we can't take their address anyway.

>

> Bootstrapped/regtested on x86_64-linux, ok for trunk?

>

> 2018-03-23  Marek Polacek  <polacek@redhat.com>

>

>         PR c++/85033

>         * semantics.c (finish_offsetof): Don't allow CONST_DECLs.

>

>         * g++.dg/ext/builtin-offsetof2.C: New test.

>

> diff --git gcc/cp/semantics.c gcc/cp/semantics.c

> index 97fa57ae94e..035e3951574 100644

> --- gcc/cp/semantics.c

> +++ gcc/cp/semantics.c

> @@ -4072,6 +4072,11 @@ finish_offsetof (tree object_ptr, tree expr, location_t loc)

>         }

>        return error_mark_node;

>      }

> +  if (TREE_CODE (expr) == CONST_DECL)

> +    {

> +      error ("cannot apply %<offsetof%> to an enumerator %qD", expr);

> +      return error_mark_node;

> +    }

>    if (REFERENCE_REF_P (expr))

>      expr = TREE_OPERAND (expr, 0);

>    if (!complete_type_or_else (TREE_TYPE (TREE_TYPE (object_ptr)), object_ptr))

> diff --git gcc/testsuite/g++.dg/ext/builtin-offsetof2.C gcc/testsuite/g++.dg/ext/builtin-offsetof2.C

> index e69de29bb2d..07cc55a65c1 100644

> --- gcc/testsuite/g++.dg/ext/builtin-offsetof2.C

> +++ gcc/testsuite/g++.dg/ext/builtin-offsetof2.C

> @@ -0,0 +1,7 @@

> +// PR c++/85033

> +

> +struct S {

> +  enum { E };

> +};

> +

> +int b = __builtin_offsetof(S, E); // { dg-error "cannot apply .offsetof. to an enumerator" }

>

>         Marek

Patch

diff --git gcc/cp/semantics.c gcc/cp/semantics.c
index 97fa57ae94e..035e3951574 100644
--- gcc/cp/semantics.c
+++ gcc/cp/semantics.c
@@ -4072,6 +4072,11 @@  finish_offsetof (tree object_ptr, tree expr, location_t loc)
 	}
       return error_mark_node;
     }
+  if (TREE_CODE (expr) == CONST_DECL)
+    {
+      error ("cannot apply %<offsetof%> to an enumerator %qD", expr);
+      return error_mark_node;
+    }
   if (REFERENCE_REF_P (expr))
     expr = TREE_OPERAND (expr, 0);
   if (!complete_type_or_else (TREE_TYPE (TREE_TYPE (object_ptr)), object_ptr))
diff --git gcc/testsuite/g++.dg/ext/builtin-offsetof2.C gcc/testsuite/g++.dg/ext/builtin-offsetof2.C
index e69de29bb2d..07cc55a65c1 100644
--- gcc/testsuite/g++.dg/ext/builtin-offsetof2.C
+++ gcc/testsuite/g++.dg/ext/builtin-offsetof2.C
@@ -0,0 +1,7 @@ 
+// PR c++/85033
+
+struct S {
+  enum { E };
+};
+
+int b = __builtin_offsetof(S, E); // { dg-error "cannot apply .offsetof. to an enumerator" }