re PR c++/50608 (cannot apply 'offsetof' to a non-constant address)

2011-11-04  Eric Botcazou  <ebotcazou@adacore.com>

	PR c++/50608
	* c-parser.c (c_parser_postfix_expression) <RID_OFFSETOF>: Adjust call
	to fold_offsetof.
	* c-typeck.c (build_unary_op) <ADDR_EXPR>: Call fold_offsetof_1.
c-family/
	* c-common.c (c_fully_fold_internal) <ADDR_EXPR>: Call fold_offsetof_1.
	(fold_offsetof_1): Make global.  Remove STOP_REF argument and adjust.
	<INDIRECT_REF>: Return the argument.
	<ARRAY_REF>: Remove special code for negative offset.
	Call fold_build_pointer_plus instead of size_binop.
	(fold_offsetof): Remove STOP_REF argument and adjust.
	* c-common.h (fold_offsetof_1): Declare.
	(fold_offsetof): Remove STOP_REF argument.
cp/
	* semantics.c (finish_offsetof): Adjust call to fold_offsetof.
	* typeck.c (cp_build_addr_expr_1): Call fold_offsetof_1.

From-SVN: r180986

11 files changed, 75 insertions, 46 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2b9e5b3..c0bdc1a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,16 +1,23 @@
-2011-11-05  Alan Modra  <amodra@gmail.com>
+2011-11-04  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR c++/50608
+	* c-parser.c (c_parser_postfix_expression) <RID_OFFSETOF>: Adjust call
+	to fold_offsetof.
+	* c-typeck.c (build_unary_op) <ADDR_EXPR>: Call fold_offsetof_1.
+
+2011-11-04  Alan Modra  <amodra@gmail.com>
 
 	* reload1.c (gen_reload): Don't use REGNO on SUBREGs.
 	* print-rtl.c (print_rtx): Don't segfault on negative regno.
 
-2011-11-03  David S. Miller  <davem@davemloft.net>
+2011-11-04  David S. Miller  <davem@davemloft.net>
 
 	PR target/49965
 	* config/sparc/sparc.c (sparc_expand_conditional_move): Handle the
 	fact that sparc_emit_float_lib_cmp modifies the comparison in
 	operands[1].
 
-2011-11-05	Ralf Corsépius <ralf.corsepius@rtems.org>
+2011-11-04  Ralf Corsépius <ralf.corsepius@rtems.org>
 
 	* config/lm32/t-rtems: New.
 	* config.gcc (lm32-*-rtems*): Add t-rtems.
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 4a452c3..d7ff089 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,15 @@
+2011-11-04  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR c++/50608
+	* c-common.c (c_fully_fold_internal) <ADDR_EXPR>: Call fold_offsetof_1.
+	(fold_offsetof_1): Make global.  Remove STOP_REF argument and adjust.
+	<INDIRECT_REF>: Return the argument.
+	<ARRAY_REF>: Remove special code for negative offset.
+	Call fold_build_pointer_plus instead of size_binop.
+	(fold_offsetof): Remove STOP_REF argument and adjust.
+	* c-common.h (fold_offsetof_1): Declare.
+	(fold_offsetof): Remove STOP_REF argument.
+
 2011-11-02  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/50810
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 2eefe03..df8dda4 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -1274,12 +1274,7 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands,
 	  && (op1 = get_base_address (op0)) != NULL_TREE
 	  && TREE_CODE (op1) == INDIRECT_REF
 	  && TREE_CONSTANT (TREE_OPERAND (op1, 0)))
-	{
-	  tree offset = fold_offsetof (op0, op1);
-	  op1
-	    = fold_convert_loc (loc, TREE_TYPE (expr), TREE_OPERAND (op1, 0));
-	  ret = fold_build_pointer_plus_loc (loc, op1, offset);
-	}
+	ret = fold_convert_loc (loc, TREE_TYPE (expr), fold_offsetof_1 (op0));
       else if (op0 != orig_op0 || in_init)
 	ret = in_init
 	  ? fold_build1_initializer_loc (loc, code, TREE_TYPE (expr), op0)
@@ -8538,20 +8533,15 @@ c_common_to_target_charset (HOST_WIDE_INT c)
     return uc;
 }
 
-/* Build the result of __builtin_offsetof.  EXPR is a nested sequence of
-   component references, with STOP_REF, or alternatively an INDIRECT_REF of
-   NULL, at the bottom; much like the traditional rendering of offsetof as a
-   macro.  Returns the folded and properly cast result.  */
+/* Fold an offsetof-like expression.  EXPR is a nested sequence of component
+   references with an INDIRECT_REF of a constant at the bottom; much like the
+   traditional rendering of offsetof as a macro.  Return the folded result.  */
 
-static tree
-fold_offsetof_1 (tree expr, tree stop_ref)
+tree
+fold_offsetof_1 (tree expr)
 {
-  enum tree_code code = PLUS_EXPR;
   tree base, off, t;
 
-  if (expr == stop_ref && TREE_CODE (expr) != ERROR_MARK)
-    return size_zero_node;
-
   switch (TREE_CODE (expr))
     {
     case ERROR_MARK:
@@ -8568,15 +8558,15 @@ fold_offsetof_1 (tree expr, tree stop_ref)
 
     case NOP_EXPR:
     case INDIRECT_REF:
-      if (!integer_zerop (TREE_OPERAND (expr, 0)))
+      if (!TREE_CONSTANT (TREE_OPERAND (expr, 0)))
 	{
 	  error ("cannot apply %<offsetof%> to a non constant address");
 	  return error_mark_node;
 	}
-      return size_zero_node;
+      return TREE_OPERAND (expr, 0);
 
     case COMPONENT_REF:
-      base = fold_offsetof_1 (TREE_OPERAND (expr, 0), stop_ref);
+      base = fold_offsetof_1 (TREE_OPERAND (expr, 0));
       if (base == error_mark_node)
 	return base;
 
@@ -8594,21 +8584,14 @@ fold_offsetof_1 (tree expr, tree stop_ref)
       break;
 
     case ARRAY_REF:
-      base = fold_offsetof_1 (TREE_OPERAND (expr, 0), stop_ref);
+      base = fold_offsetof_1 (TREE_OPERAND (expr, 0));
       if (base == error_mark_node)
 	return base;
 
       t = TREE_OPERAND (expr, 1);
-      if (TREE_CODE (t) == INTEGER_CST && tree_int_cst_sgn (t) < 0)
-	{
-	  code = MINUS_EXPR;
-	  t = fold_build1_loc (input_location, NEGATE_EXPR, TREE_TYPE (t), t);
-	}
-      t = convert (sizetype, t);
-      off = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (TREE_TYPE (expr)), t);
 
       /* Check if the offset goes beyond the upper bound of the array.  */
-      if (code == PLUS_EXPR && TREE_CODE (t) == INTEGER_CST)
+      if (TREE_CODE (t) == INTEGER_CST && tree_int_cst_sgn (t) >= 0)
 	{
 	  tree upbound = array_ref_up_bound (expr);
 	  if (upbound != NULL_TREE
@@ -8648,26 +8631,30 @@ fold_offsetof_1 (tree expr, tree stop_ref)
 		}
 	    }
 	}
+
+      t = convert (sizetype, t);
+      off = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (TREE_TYPE (expr)), t);
       break;
 
     case COMPOUND_EXPR:
       /* Handle static members of volatile structs.  */
       t = TREE_OPERAND (expr, 1);
       gcc_assert (TREE_CODE (t) == VAR_DECL);
-      return fold_offsetof_1 (t, stop_ref);
+      return fold_offsetof_1 (t);
 
     default:
       gcc_unreachable ();
     }
 
-  return size_binop (code, base, off);
+  return fold_build_pointer_plus (base, off);
 }
 
+/* Likewise, but convert it to the return type of offsetof.  */
+
 tree
-fold_offsetof (tree expr, tree stop_ref)
+fold_offsetof (tree expr)
 {
-  /* Convert back from the internal sizetype to size_t.  */
-  return convert (size_type_node, fold_offsetof_1 (expr, stop_ref));
+  return convert (size_type_node, fold_offsetof_1 (expr));
 }
 
 /* Warn for A ?: C expressions (with B omitted) where A is a boolean 
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 71746a9..7ecb57e 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -956,7 +956,8 @@ extern bool c_dump_tree (void *, tree);
 
 extern void verify_sequence_points (tree);
 
-extern tree fold_offsetof (tree, tree);
+extern tree fold_offsetof_1 (tree);
+extern tree fold_offsetof (tree);
 
 /* Places where an lvalue, or modifiable lvalue, may be required.
    Used to select diagnostic messages in lvalue_error and
diff --git a/gcc/c-parser.c b/gcc/c-parser.c
index af6cc14..8db203a 100644
--- a/gcc/c-parser.c
+++ b/gcc/c-parser.c
@@ -6388,7 +6388,7 @@ c_parser_postfix_expression (c_parser *parser)
 	      c_parser_error (parser, "expected identifier");
 	    c_parser_skip_until_found (parser, CPP_CLOSE_PAREN,
 				       "expected %<)%>");
-	    expr.value = fold_offsetof (offsetof_ref, NULL_TREE);
+	    expr.value = fold_offsetof (offsetof_ref);
 	  }
 	  break;
 	case RID_CHOOSE_EXPR:
diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index 7dfdae2..46363c0 100644
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -3890,10 +3890,7 @@ build_unary_op (location_t location,
       if (val && TREE_CODE (val) == INDIRECT_REF
           && TREE_CONSTANT (TREE_OPERAND (val, 0)))
 	{
-	  tree op0 = fold_offsetof (arg, val), op1;
-
-	  op1 = fold_convert_loc (location, argtype, TREE_OPERAND (val, 0));
-	  ret = fold_build_pointer_plus_loc (location, op1, op0);
+	  ret = fold_convert_loc (location, argtype, fold_offsetof_1 (arg));
 	  goto return_build_unary_op;
 	}
 
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2a1db7a..ffb085c 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2011-11-04  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR c++/50608
+	* semantics.c (finish_offsetof): Adjust call to fold_offsetof.
+	* typeck.c (cp_build_addr_expr_1): Call fold_offsetof_1.
+
 2011-11-04  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* typeck.c (build_indirect_ref): Use ATTRIBUTE_UNUSED.
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index a80aec6..cebb7df 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3568,7 +3568,7 @@ finish_offsetof (tree expr)
       if (!complete_type_or_else (TREE_TYPE (object), object))
 	return error_mark_node;
     }
-  return fold_offsetof (expr, NULL_TREE);
+  return fold_offsetof (expr);
 }
 
 /* Replace the AGGR_INIT_EXPR at *TP with an equivalent CALL_EXPR.  This
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index f4e45b4..386f3b8 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -4881,9 +4881,7 @@ cp_build_addr_expr_1 (tree arg, bool strict_lvalue, tsubst_flags_t complain)
       && TREE_CONSTANT (TREE_OPERAND (val, 0)))
     {
       tree type = build_pointer_type (argtype);
-      tree op0 = fold_convert (type, TREE_OPERAND (val, 0));
-      tree op1 = fold_offsetof (arg, val);
-      return fold_build_pointer_plus (op0, op1);
+      return fold_convert (type, fold_offsetof_1 (arg));
     }
 
   /* Handle complex lvalues (when permitted)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e39ed46..218a9d3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2011-11-04  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* g++.dg/other/offsetof7.C: New test.
+
 2011-11-04  Hans-Peter Nilsson  <hp@axis.com>
 
 	* lib/gcc-dg.exp (gcc_force_conventional_output): New global
diff --git a/gcc/testsuite/g++.dg/other/offsetof7.C b/gcc/testsuite/g++.dg/other/offsetof7.C
new file mode 100644
index 0000000..0ce2ee0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/offsetof7.C
@@ -0,0 +1,17 @@
+// PR c++/50608
+// Testcase by <dberger@oubliette.org>
+// { dg-do compile }
+
+struct A {
+    int offset;
+};
+
+struct B: public A {
+};
+
+struct C {
+    A a;
+    B b;
+};
+
+int fails = __builtin_offsetof (C, b.offset);