[PATCH] c++: Fix -fstrong-eval-order for operator &&, || and , [PR82959]

[Jakub Jelinek via Gcc-patches]

Hi!

P0145R3 added
"However, the operands are sequenced in the order prescribed for the built-in
operator" rule for overloaded operator calls when using the operator syntax.
op_is_ordered follows that, but added just the overloaded operators
added in that paper.  &&, || and comma operators had rules that
lhs is sequenced before rhs already in C++98.
The following patch adds those cases to op_is_ordered.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2021-03-02  Jakub Jelinek  <ja...@redhat.com>

        PR c++/82959
        * call.c (op_is_ordered): Handle TRUTH_ANDIF_EXPR, TRUTH_ORIF_EXPR
        and COMPOUND_EXPR.

        * g++.dg/cpp1z/eval-order10.C: New test.

--- gcc/cp/call.c.jj    2021-02-19 12:14:10.965113839 +0100
+++ gcc/cp/call.c       2021-03-02 13:32:08.423924095 +0100
@@ -6083,6 +6083,15 @@ op_is_ordered (tree_code code)
     case LSHIFT_EXPR:
       // 8. a >> b
     case RSHIFT_EXPR:
+      // a && b
+      // Predates P0145R3.
+    case TRUTH_ANDIF_EXPR:
+      // a || b
+      // Predates P0145R3.
+    case TRUTH_ORIF_EXPR:
+      // a , b
+      // Predates P0145R3.
+    case COMPOUND_EXPR:
       return (flag_strong_eval_order ? 1 : 0);
 
     default:
--- gcc/testsuite/g++.dg/cpp1z/eval-order10.C.jj        2021-03-02 
14:15:21.735278240 +0100
+++ gcc/testsuite/g++.dg/cpp1z/eval-order10.C   2021-03-02 14:24:36.984143267 
+0100
@@ -0,0 +1,27 @@
+// PR c++/82959
+// { dg-do run }
+// { dg-additional-options -fstrong-eval-order }
+
+struct A {};
+
+void operator && (const A x, const A) {}
+void operator || (const A x, const A) {}
+void operator , (const A x, const A) {}
+
+int i;
+
+A f () { if (i != 0) __builtin_abort (); i = 1; return A (); }
+A g () { if (i != 1) __builtin_abort (); i = 2; return A (); }
+
+int
+main ()
+{
+  f () && g ();
+  if (i != 2) __builtin_abort ();
+  i = 0;
+  f () || g ();
+  if (i != 2) __builtin_abort ();
+  i = 0;
+  f (), g ();
+  if (i != 2) __builtin_abort ();
+}

        Jakub