P0145R2: Refining Expression Order for C++ (complex LHS of =).

gcc/c-common/
	* c-common.c (verify_tree) [COMPOUND_EXPR]: Fix handling on LHS of
	MODIFY_EXPR.
gcc/cp/
	* typeck.c (cp_build_modify_expr): Leave COMPOUND_EXPR on LHS.

git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@237775 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 19 insertions, 22 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 16e55726976..86ce14a968e 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,9 @@
+2016-06-24  Jason Merrill  <jason@redhat.com>
+
+	P0145R2: Refining Expression Order for C++.
+	* c-common.c (verify_tree) [COMPOUND_EXPR]: Fix handling on LHS of
+	MODIFY_EXPR.
+
 2016-06-24  Jakub Jelinek  <jakub@redhat.com>
 
 	* c-common.c (check_builtin_function_arguments): Require last
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 4988f066eb2..3301c313998 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -2980,13 +2980,15 @@ verify_tree (tree x, struct tlist **pbefore_sp, struct tlist **pno_sp,
     case COMPOUND_EXPR:
     case TRUTH_ANDIF_EXPR:
     case TRUTH_ORIF_EXPR:
-      tmp_before = tmp_nosp = tmp_list3 = 0;
+      tmp_before = tmp_nosp = tmp_list2 = tmp_list3 = 0;
       verify_tree (TREE_OPERAND (x, 0), &tmp_before, &tmp_nosp, NULL_TREE);
       warn_for_collisions (tmp_nosp);
       merge_tlist (pbefore_sp, tmp_before, 0);
       merge_tlist (pbefore_sp, tmp_nosp, 0);
-      verify_tree (TREE_OPERAND (x, 1), &tmp_list3, pno_sp, NULL_TREE);
+      verify_tree (TREE_OPERAND (x, 1), &tmp_list3, &tmp_list2, NULL_TREE);
+      warn_for_collisions (tmp_list2);
       merge_tlist (pbefore_sp, tmp_list3, 0);
+      merge_tlist (pno_sp, tmp_list2, 0);
       return;
 
     case COND_EXPR:
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a36cbff0a32..33e10baf9f1 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2016-06-24  Jason Merrill  <jason@redhat.com>
 
+	P0145R2: Refining Expression Order for C++.
+	* typeck.c (cp_build_modify_expr): Leave COMPOUND_EXPR on LHS.
+
 	* tree.c (get_target_expr_sfinae): Handle bit-fields.
 	(build_target_expr): Call mark_rvalue_use.
 
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 3704b884473..fb6a16e00c6 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -7515,7 +7515,8 @@ cp_build_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
   if (error_operand_p (lhs) || error_operand_p (rhs))
     return error_mark_node;
 
-  /* Handle control structure constructs used as "lvalues".  */
+  /* Handle control structure constructs used as "lvalues".  Note that we
+     leave COMPOUND_EXPR on the LHS because it is sequenced after the RHS.  */
   switch (TREE_CODE (lhs))
     {
       /* Handle --foo = 5; as these are valid constructs in C++.  */
@@ -7525,31 +7526,16 @@ cp_build_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
 	lhs = build2 (TREE_CODE (lhs), TREE_TYPE (lhs),
 		      cp_stabilize_reference (TREE_OPERAND (lhs, 0)),
 		      TREE_OPERAND (lhs, 1));
-      newrhs = cp_build_modify_expr (loc, TREE_OPERAND (lhs, 0),
-				     modifycode, rhs, complain);
-      if (newrhs == error_mark_node)
-	return error_mark_node;
-      return build2 (COMPOUND_EXPR, lhstype, lhs, newrhs);
-
-      /* Handle (a, b) used as an "lvalue".  */
-    case COMPOUND_EXPR:
-      newrhs = cp_build_modify_expr (loc, TREE_OPERAND (lhs, 1),
-				     modifycode, rhs, complain);
-      if (newrhs == error_mark_node)
-	return error_mark_node;
-      return build2 (COMPOUND_EXPR, lhstype,
-		     TREE_OPERAND (lhs, 0), newrhs);
+      lhs = build2 (COMPOUND_EXPR, lhstype, lhs, TREE_OPERAND (lhs, 0));
+      break;
 
     case MODIFY_EXPR:
       if (TREE_SIDE_EFFECTS (TREE_OPERAND (lhs, 0)))
 	lhs = build2 (TREE_CODE (lhs), TREE_TYPE (lhs),
 		      cp_stabilize_reference (TREE_OPERAND (lhs, 0)),
 		      TREE_OPERAND (lhs, 1));
-      newrhs = cp_build_modify_expr (loc, TREE_OPERAND (lhs, 0), modifycode,
-				     rhs, complain);
-      if (newrhs == error_mark_node)
-	return error_mark_node;
-      return build2 (COMPOUND_EXPR, lhstype, lhs, newrhs);
+      lhs = build2 (COMPOUND_EXPR, lhstype, lhs, TREE_OPERAND (lhs, 0));
+      break;
 
     case MIN_EXPR:
     case MAX_EXPR: