re PR c++/85437 (member pointer static upcast rejected in a constexpr context)

PR c++/85437
	PR c++/49171
	* cp-tree.h (REINTERPRET_CAST_P): New.
	* constexpr.c (cxx_eval_constant_expression) <case NOP_EXPR>:
	Reject REINTERPET_CAST_P conversions.  Use cplus_expand_constant
	for non-trivial PTRMEM_CST cases.
	* typeck.c (build_nop_reinterpret): New.
	(build_reinterpret_cast_1): Use it.  Set REINTERPRET_CAST_P on
	NOP_EXPRs returned by cp_convert.

	* g++.dg/cpp0x/addressof1.C: Make reinterpret cases runtime checks.
	* g++.dg/cpp0x/constexpr-cast.C: Remove xfails
	* g++.dg/cpp0x/constexpr-nullptr-2.C: Likewise.
	* g++.dg/cpp0x/constexpr-pmf1.C: Check when optimized.
	* g++.dg/cpp0x/pr85437-1.C: New.
	* g++.dg/cpp0x/pr85437-2.C: New.
	* g++.dg/cpp0x/pr85437-3.C: New.
	* g++.dg/cpp0x/pr85437-4.C: New.

From-SVN: r259629

gcc/cp/ChangeLog

@@ -1,3 +1,15 @@
+2018-04-25  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/85437
+	PR c++/49171
+	* cp-tree.h (REINTERPRET_CAST_P): New.
+	* constexpr.c (cxx_eval_constant_expression) <case NOP_EXPR>:
+	Reject REINTERPET_CAST_P conversions.  Use cplus_expand_constant
+	for non-trivial PTRMEM_CST cases.
+	* typeck.c (build_nop_reinterpret): New.
+	(build_reinterpret_cast_1): Use it.  Set REINTERPRET_CAST_P on
+	NOP_EXPRs returned by cp_convert.
+
 2018-04-23  Jason Merrill  <jason@redhat.com>
 
 	PR c++/69560 - wrong alignof(double) on x86.

gcc/cp/constexpr.c

@@ -1822,8 +1822,8 @@ reduced_constant_expression_p (tree t)
 }
 
 /* Some expressions may have constant operands but are not constant
-   themselves, such as 1/0.  Call this function (or rather, the macro
+   themselves, such as 1/0.  Call this function to check for that
-   following it) to check for that condition.
+   condition.
 
    We only call this in places that require an arithmetic constant, not in
    places where we might have a non-constant expression that can be a
@@ -4579,9 +4579,18 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 				       non_constant_p, overflow_p);
       break;
 
+    case NOP_EXPR:
+      if (REINTERPRET_CAST_P (t))
+	{
+	  if (!ctx->quiet)
+	    error_at (EXPR_LOC_OR_LOC (t, input_location),
+		      "a reinterpret_cast is not a constant expression");
+	  *non_constant_p = true;
+	  return t;
+	}
+      /* FALLTHROUGH.  */
     case CONVERT_EXPR:
     case VIEW_CONVERT_EXPR:
-    case NOP_EXPR:
     case UNARY_PLUS_EXPR:
       {
 	tree oldop = TREE_OPERAND (t, 0);
@@ -4595,20 +4604,13 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 	if (TREE_CODE (op) == PTRMEM_CST
 	    && !TYPE_PTRMEM_P (type))
 	  op = cplus_expand_constant (op);
+
 	if (TREE_CODE (op) == PTRMEM_CST && tcode == NOP_EXPR)
 	  {
-	    if (same_type_ignoring_top_level_qualifiers_p (type,
+	    if (!same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (op))
-							   TREE_TYPE (op))
+		&& !can_convert_qual (type, op))
-		|| can_convert_qual (type, op))
+	      op = cplus_expand_constant (op);
 	    return cp_fold_convert (type, op);
-	    else
-	      {
-		if (!ctx->quiet)
-		  error_at (EXPR_LOC_OR_LOC (t, input_location),
-			    "a reinterpret_cast is not a constant expression");
-		*non_constant_p = true;
-		return t;
-	      }
 	  }
 
 	if (POINTER_TYPE_P (type) && TREE_CODE (op) == INTEGER_CST)
@@ -4653,14 +4655,17 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 		return t;
 	      }
 	  }
+
 	if (op == oldop && tcode != UNARY_PLUS_EXPR)
 	  /* We didn't fold at the top so we could check for ptr-int
 	     conversion.  */
 	  return fold (t);
+
 	if (tcode == UNARY_PLUS_EXPR)
 	  r = fold_convert (TREE_TYPE (t), op);
 	else
 	  r = fold_build1 (tcode, type, op);
+
 	/* Conversion of an out-of-range value has implementation-defined
 	   behavior; the language considers it different from arithmetic
 	   overflow, which is undefined.  */

gcc/cp/cp-tree.h

@@ -372,6 +372,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
       TEMPLATE_TYPE_PARM_FOR_CLASS (TEMPLATE_TYPE_PARM)
       DECL_NAMESPACE_INLINE_P (in NAMESPACE_DECL)
       SWITCH_STMT_ALL_CASES_P (in SWITCH_STMT)
+      REINTERPRET_CAST_P (in NOP_EXPR)
       ALIGNOF_EXPR_STD_P (in ALIGNOF_EXPR)
    1: IDENTIFIER_KIND_BIT_1 (in IDENTIFIER_NODE)
       TI_PENDING_TEMPLATE_FLAG.
@@ -632,6 +633,11 @@ typedef struct ptrmem_cst * ptrmem_cst_t;
 #define COND_EXPR_IS_VEC_DELETE(NODE) \
   TREE_LANG_FLAG_0 (COND_EXPR_CHECK (NODE))
 
+/* Nonzero if this NOP_EXPR is a reinterpret_cast.  Such conversions
+   are not constexprs.  Other NOP_EXPRs are.  */
+#define REINTERPRET_CAST_P(NODE)		\
+  TREE_LANG_FLAG_0 (NOP_EXPR_CHECK (NODE))
+
 /* Returns nonzero iff TYPE1 and TYPE2 are the same type, in the usual
    sense of `same'.  */
 #define same_type_p(TYPE1, TYPE2) \

gcc/cp/typeck.c

@@ -7280,6 +7280,18 @@ convert_member_func_to_ptr (tree type, tree expr, tsubst_flags_t complain)
   return build_nop (type, expr);
 }
 
+/* Build a NOP_EXPR to TYPE, but mark it as a reinterpret_cast so that
+   constexpr evaluation knows to reject it.  */
+
+static tree
+build_nop_reinterpret (tree type, tree expr)
+{
+  tree ret = build_nop (type, expr);
+  if (ret != expr)
+    REINTERPRET_CAST_P (ret) = true;
+  return ret;
+}
+
 /* Return a representation for a reinterpret_cast from EXPR to TYPE.
    If C_CAST_P is true, this reinterpret cast is being done as part of
    a C-style cast.  If VALID_P is non-NULL, *VALID_P is set to
@@ -7414,7 +7426,7 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
 	warning (OPT_Wcast_function_type,
 		 "cast between incompatible function types"
 		 " from %qH to %qI", intype, type);
-      return build_nop (type, expr);
+      return build_nop_reinterpret (type, expr);
     }
   else if (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype))
     {
@@ -7425,7 +7437,7 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
 	warning (OPT_Wcast_function_type,
 		 "cast between incompatible pointer to member types"
 		 " from %qH to %qI", intype, type);
-      return build_nop (type, expr);
+      return build_nop_reinterpret (type, expr);
     }
   else if ((TYPE_PTRDATAMEM_P (type) && TYPE_PTRDATAMEM_P (intype))
 	   || (TYPE_PTROBV_P (type) && TYPE_PTROBV_P (intype)))
@@ -7451,7 +7463,7 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
 	/* strict_aliasing_warning STRIP_NOPs its expr.  */
 	strict_aliasing_warning (EXPR_LOCATION (expr), type, expr);
 
-      return build_nop (type, expr);
+      return build_nop_reinterpret (type, expr);
     }
   else if ((TYPE_PTRFN_P (type) && TYPE_PTROBV_P (intype))
 	   || (TYPE_PTRFN_P (intype) && TYPE_PTROBV_P (type)))
@@ -7462,7 +7474,7 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
 	warning (OPT_Wconditionally_supported,
 		 "casting between pointer-to-function and pointer-to-object "
 		 "is conditionally-supported");
-      return build_nop (type, expr);
+      return build_nop_reinterpret (type, expr);
     }
   else if (VECTOR_TYPE_P (type))
     return convert_to_vector (type, expr);
@@ -7478,7 +7490,11 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
       return error_mark_node;
     }
 
-  return cp_convert (type, expr, complain);
+  expr = cp_convert (type, expr, complain);
+  if (TREE_CODE (expr) == NOP_EXPR)
+    /* Mark any nop_expr that created as a reintepret_cast.  */
+    REINTERPRET_CAST_P (expr) = true;
+  return expr;
 }
 
 tree

gcc/testsuite/ChangeLog

@@ -1,3 +1,17 @@
+2018-04-25  Nathan Sidwell  <nathan@acm.org>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/85437
+	PR c++/49171
+	* g++.dg/cpp0x/addressof1.C: Make reinterpret cases runtime checks.
+	* g++.dg/cpp0x/constexpr-cast.C: Remove xfails
+	* g++.dg/cpp0x/constexpr-nullptr-2.C: Likewise.
+	* g++.dg/cpp0x/constexpr-pmf1.C: Check when optimized.
+	* g++.dg/cpp0x/pr85437-1.C: New.
+	* g++.dg/cpp0x/pr85437-2.C: New.
+	* g++.dg/cpp0x/pr85437-3.C: New.
+	* g++.dg/cpp0x/pr85437-4.C: New.
+
 2018-04-24  Steven G. Kargl  <kargl@gcc.gnu.org>
 
 	PR fortran/85520
@@ -8,6 +22,7 @@
 	PR target/85512
 	* gcc.dg/pr85512.c: New test.
 
+2018-04-24  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR target/85485
 	* g++.dg/cet-notrack-1.C (dg-options): Remove -mcet.

gcc/testsuite/g++.dg/cpp0x/addressof1.C

@@ -18,9 +18,7 @@ static_assert (addressof (j) == &i, "");
 
 struct S { int s; } s;
 static_assert (__builtin_addressof (s) == &s, "");
-static_assert ((int *) __builtin_addressof (s) == &s.s, "");
 static_assert (addressof (s) == &s, "");
-static_assert ((int *) addressof (s) == &s.s, "");
 
 struct T
 {
@@ -31,9 +29,7 @@ struct T
 };
 constexpr T t;
 T T::tt;
-static_assert (__builtin_addressof (t) == (const T *) &t.p, "");
 static_assert (&t == __builtin_addressof (T::tt), "");
-static_assert (addressof (t) == (const T *) &t.p, "");
 static_assert (&t == addressof (T::tt), "");
 
 struct S x, y;
@@ -76,8 +72,6 @@ constexpr int a = 1;
 static_assert (__builtin_addressof (a) == &a, "");
 static_assert (addressof (a) == &a, "");
 constexpr int c[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
-static_assert ((const int *) __builtin_addressof (c) == &c[0], "");
-static_assert ((const int *) addressof (c) == &c[0], "");
 
 void
 baz ()
@@ -93,4 +87,15 @@ main ()
       || __builtin_addressof (baz) != baz
       || addressof (baz) != baz)
     __builtin_abort ();
+
+  // reinterpret casts are not constexprs
+  if (! (((int *) __builtin_addressof (s) == &s.s)
+	 && ((int *) addressof (s) == &s.s)
+	 && (__builtin_addressof (t) == (const T *) &t.p)
+	 && (addressof (t) == (const T *) &t.p)
+	 && ((const int *) __builtin_addressof (c) == &c[0])
+	 && ((const int *) addressof (c) == &c[0])))
+    __builtin_abort ();
+
+  return 0;
 }

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

@@ -4,8 +4,8 @@
 
 int i;
 
-// The following is accepted due to bug 49171.
+// The following was accepted due to bug 49171.
-constexpr void *q = reinterpret_cast<void*>(&i);    // { dg-error "" "bug c++/49171" { xfail *-*-* } }
+constexpr void *q = reinterpret_cast<void*>(&i);    // { dg-error "not a constant expression" }
 
 constexpr void *r0 = reinterpret_cast<void*>(1);    // { dg-error "not a constant expression|reinterpret_cast from integer to pointer" }
 constexpr void *r1 = reinterpret_cast<void*>(sizeof 'x');  // { dg-error ".reinterpret_cast<void\\*>\\(1\[ul\]\*\\). is not a constant expression" }

gcc/testsuite/g++.dg/cpp0x/constexpr-nullptr-2.C

@@ -99,9 +99,8 @@ constexpr const volatile void* pv3 = p0;
 constexpr void* pv4 = static_cast<void*>(p0);
 constexpr const void* pv5 = static_cast<const void*>(p0);
 
-// The following should be rejected but isn't because of bug c++/49171
+// The following was accepted due to bug c++/49171
-// - [C++0x][constexpr] Constant expressions support reinterpret_cast
+constexpr void* pv6 = reinterpret_cast<void*>(p0);   // { dg-error "not a constant expression" }
-constexpr void* pv6 = reinterpret_cast<void*>(p0);   // { dg-error "" "bug c++/49171" { xfail *-*-* } }
 
 // Adding or subtracting zero from a null pointer is valid in C++.
 constexpr int* p1 = p0 + 0;

gcc/testsuite/g++.dg/cpp0x/constexpr-pmf1.C

@@ -1,6 +1,6 @@
 // PR c++/77775
-// { dg-options -fdump-tree-gimple }
+// { dg-options "-fdump-tree-fre1 -O1" }
-// { dg-final { scan-tree-dump "== viewAdded" "gimple" { target c++11 } } }
+// { dg-final { scan-tree-dump "== viewAdded" "fre1" { target c++11 } } }
 
 namespace Sublime {
 struct View;

gcc/testsuite/g++.dg/cpp0x/pr85437-1.C

@@ -0,0 +1,17 @@
+// PR c++/85437
+// { dg-do compile { target c++11 } }
+
+struct A { int a; constexpr A() : a(0) {} };
+struct B : A { int x; constexpr B() : x(0) {} };
+struct X { int z; constexpr X() : z(0) {} };
+struct C : X, B {};
+constexpr int C::*cbx = &B::x;
+constexpr int B::*bx = &B::x;
+constexpr int A::*abx = static_cast<int(A::*)>(&B::x);	// { dg-bogus "not a constant expression" }
+
+constexpr const C y;
+constexpr const B& yb = y;
+constexpr const A& ya = y;
+constexpr int const *pcbx = &(y.*cbx);
+constexpr int const *pbx = &(y.*bx);
+constexpr int const *pabx = &(ya.*abx);

gcc/testsuite/g++.dg/cpp0x/pr85437-2.C

@@ -0,0 +1,8 @@
+// PR c++/85437
+// { dg-do compile { target c++11 } }
+
+struct A { };
+struct B : A { int x; };
+
+constexpr int A::*abx
+= reinterpret_cast<int(A::*)>(&B::x); // { dg-error "reinterpret.*constant" }

gcc/testsuite/g++.dg/cpp0x/pr85437-3.C

@@ -0,0 +1,8 @@
+// PR c++/85437
+// { dg-do compile { target c++11 } }
+
+struct A { int y; };
+struct B { int x; };
+struct C : A, B {};
+constexpr int C::*pci = &B::x;
+constexpr int A::*pai = static_cast<int A::*>(static_cast<int C::*>(&B::x)); // { dg-bogus "not a constant expression" }

gcc/testsuite/g++.dg/cpp0x/pr85437-4.C

@@ -0,0 +1,8 @@
+// PR c++/85437
+// { dg-do compile { target c++11 } }
+
+struct A { };
+struct B { int x; };
+struct C : A, B {};
+constexpr int C::*pci = &B::x;
+constexpr int A::*pai = static_cast<int A::*>(pci);	// { dg-bogus "not a constant expression" }