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* [gcc r12-9989] c++: fix contracts with NRV
@ 2023-11-17  0:21 Jason Merrill
  0 siblings, 0 replies; only message in thread
From: Jason Merrill @ 2023-11-17  0:21 UTC (permalink / raw)
  To: gcc-cvs

https://gcc.gnu.org/g:11afe64fb71c83cef7d56fe6c411fb7adeee59cb

commit r12-9989-g11afe64fb71c83cef7d56fe6c411fb7adeee59cb
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Jun 5 23:58:32 2023 -0400

    c++: fix contracts with NRV
    
    The NRV implementation was blindly replacing the operand of RETURN_EXPR,
    clobbering anything that check_return_expr might have added on to the actual
    initialization, such as checking the postcondition.
    
    GCC 12 note: There are no contracts in GCC 12, but this issue also broke
    setting current_retval_sentinel.
    
    gcc/cp/ChangeLog:
    
            * semantics.cc (finalize_nrv_r): [RETURN_EXPR]: Only replace the
            INIT_EXPR.

Diff:
---
 gcc/cp/semantics.cc | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 5289131e591..d6351d2d8a3 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -4859,9 +4859,17 @@ finalize_nrv_r (tree* tp, int* walk_subtrees, void* data)
     *walk_subtrees = 0;
   /* Change all returns to just refer to the RESULT_DECL; this is a nop,
      but differs from using NULL_TREE in that it indicates that we care
-     about the value of the RESULT_DECL.  */
+     about the value of the RESULT_DECL.  But preserve anything appended
+     by check_return_expr.  */
   else if (TREE_CODE (*tp) == RETURN_EXPR)
-    TREE_OPERAND (*tp, 0) = dp->result;
+    {
+      tree *p = &TREE_OPERAND (*tp, 0);
+      while (TREE_CODE (*p) == COMPOUND_EXPR)
+	p = &TREE_OPERAND (*p, 0);
+      gcc_checking_assert (TREE_CODE (*p) == INIT_EXPR
+			   && TREE_OPERAND (*p, 0) == dp->result);
+      *p = dp->result;
+    }
   /* Change all cleanups for the NRV to only run when an exception is
      thrown.  */
   else if (TREE_CODE (*tp) == CLEANUP_STMT

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