[gcc(refs/users/aoliva/heads/testme)] c++: for contracts, cdtors never return this

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:444347c11ba38a114d3a21c271265723418d72dd

commit 444347c11ba38a114d3a21c271265723418d72dd
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Sat Nov 18 02:11:24 2023 -0300

    c++: for contracts, cdtors never return this
    
    When targetm.cxx.cdtor_return_this() holds, cdtors have a
    non-VOID_TYPE_P result, but IMHO this ABI implementation detail
    shouldn't leak to the abstract language conceptual framework, in which
    cdtors don't have return values.  For contracts, specifically those
    that establish postconditions on results, such a leakage is present,
    and the present patch puts an end to it: with it, cdtors get an error
    for result postconditions regardless of the ABI.  This fixes
    g++.dg/contracts/contracts-ctor-dtor2.C on arm-eabi.
    
    
    for  gcc/cp/ChangeLog
    
            * contracts.cc (check_postcondition_result): Cope with
            cdtor_return_this.

Diff:
---
 gcc/cp/contracts.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/contracts.cc b/gcc/cp/contracts.cc
index 66d2298a9bf..035ca4827e7 100644
--- a/gcc/cp/contracts.cc
+++ b/gcc/cp/contracts.cc
@@ -636,7 +636,11 @@ make_postcondition_variable (cp_expr id)
 bool
 check_postcondition_result (tree decl, tree type, location_t loc)
 {
-  if (VOID_TYPE_P (type))
+  /* Do not be confused by targetm.cxx.cdtor_return_this ();
+     conceptually, cdtors have no return value.  */
+  if (VOID_TYPE_P (type)
+      || DECL_CONSTRUCTOR_P (decl)
+      || DECL_DESTRUCTOR_P (decl))
     {
       error_at (loc,
 		DECL_CONSTRUCTOR_P (decl)