re PR c++/89599 (C-style function-pointer-to-void* cast is handled inconsistently)

	PR c++/89599
	* constexpr.c (potential_constant_expression_1): Reject
	REINTERPRET_CAST_P NOP_EXPRs.

	* g++.dg/ubsan/vptr-4.C: Adjust expected diagnostics.
	* g++.dg/parse/array-size2.C: Likewise.
	* g++.dg/cpp0x/constexpr-89599.C: New test.

From-SVN: r269482

gcc/cp/ChangeLog

 2019-03-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/89599
+	* constexpr.c (potential_constant_expression_1): Reject
+	REINTERPRET_CAST_P NOP_EXPRs.
+
 	PR c++/89622
 	* call.c (joust): Call print_z_candidate only if pedwarn returned
 	true.

gcc/cp/constexpr.c

@@ -5961,6 +5961,13 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
       return true;
 
     case NOP_EXPR:
+      if (REINTERPRET_CAST_P (t))
+	{
+	  if (flags & tf_error)
+	    error_at (loc, "a reinterpret_cast is not a constant expression");
+	  return false;
+	}
+      /* FALLTHRU */
     case CONVERT_EXPR:
     case VIEW_CONVERT_EXPR:
       /* -- a reinterpret_cast.  FIXME not implemented, and this rule

gcc/testsuite/ChangeLog

 2019-03-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/89599
+	* g++.dg/ubsan/vptr-4.C: Adjust expected diagnostics.
+	* g++.dg/parse/array-size2.C: Likewise.
+	* g++.dg/cpp0x/constexpr-89599.C: New test.
+
 	PR c++/89622
 	* g++.dg/warn/pr89622.C: New test.
 

gcc/testsuite/g++.dg/cpp0x/constexpr-89599.C

+// PR c++/89599
+// { dg-do compile { target c++11 } }
+
+void foo (int x) {}
+constexpr void *arr[2] = { (void*) &foo, (void *) foo };// { dg-error "a reinterpret_cast is not a constant expression" }
+constexpr void *ptr = (void *) &foo;			// { dg-error "a reinterpret_cast is not a constant expression" }

gcc/testsuite/g++.dg/parse/array-size2.C

@@ -15,6 +15,8 @@ void
 foo (void)
 {
   char g[(char *) &((struct S *) 0)->b - (char *) 0]; // { dg-error "40:size of array .g. is not an integral constant-expression" }
+						      // { dg-error "narrowing conversion" "" { target c++11 } .-1 }
+						      // { dg-message "expression has a constant value but is not a C.. constant-expression" "" { target c++11 } .-2 }
   char h[(__SIZE_TYPE__) &((struct S *) 8)->b];	      // { dg-error "10:size of array .h. is not an integral constant-expression" }
   bar (g, h);
 }

gcc/testsuite/g++.dg/ubsan/vptr-4.C

@@ -19,7 +19,7 @@ struct T : S {
 };
 
 constexpr T t;
-constexpr const T *p = t.foo ();	// { dg-message "expansion of" }
+constexpr const T *p = t.foo ();	// { dg-error "called in a constant expression" }
 
 template <typename U>
 struct V {
@@ -39,17 +39,16 @@ struct W : V<U> {
 };
 
 constexpr W<int> w;
-constexpr const W<int> *s = w.foo ();	// { dg-error "is not a constant expression" }
-// { dg-message "expansion of" "" { target *-*-* } .-1 }
+constexpr const W<int> *s = w.foo ();	// { dg-error "called in a constant expression" }
 
 template <typename U>
 int foo (void)
 {
   static constexpr T t;
-  static constexpr const T *p = t.foo ();	// { dg-message "expansion of" }
+  static constexpr const T *p = t.foo ();	// { dg-error "called in a constant expression" }
   static constexpr W<U> w;
-  static constexpr const W<U> *s = w.foo ();	// { dg-error "is not a constant expression" }
-  return t.b + w.b;				// { dg-message "expansion of" "" { target *-*-* } .-1 }
+  static constexpr const W<U> *s = w.foo ();	// { dg-error "called in a constant expression" }
+  return t.b + w.b;
 }
 
 int x = foo <char> ();