[C++ PATCH] Fix ICE with -fpermissive on post{inc,dec}rement (PR c++/79377)

[Jakub Jelinek]

Hi!

As the testcase shows, with -fpermissive we call operator++() or
operator--() if operator++(int) or operator--(int) is not available,
but the new code in build_min_non_dep_op_overload wasn't expecting
such a change.  Fixed thusly, bootstrapped/regtested on x86_64-linux
and i686-linux, ok for trunk?

2017-02-06  Jakub Jelinek  <ja...@redhat.com>

        PR c++/79377
        * tree.c (build_min_non_dep_op_overload): For POST{INC,DEC}REMENT_EXPR
        allow one fewer than expected arguments if flag_permissive.

        * g++.dg/lookup/pr79377.C: New test.

--- gcc/cp/tree.c.jj    2017-01-26 20:35:13.000000000 +0100
+++ gcc/cp/tree.c       2017-02-06 17:30:26.101413319 +0100
@@ -2938,8 +2938,10 @@ build_min_non_dep_op_overload (enum tree
   nargs = call_expr_nargs (non_dep);
 
   expected_nargs = cp_tree_code_length (op);
-  if (op == POSTINCREMENT_EXPR
-      || op == POSTDECREMENT_EXPR)
+  if ((op == POSTINCREMENT_EXPR
+       || op == POSTDECREMENT_EXPR)
+      /* With -fpermissive non_dep could be operator++().  */
+      && (!flag_permissive || nargs != expected_nargs))
     expected_nargs += 1;
   gcc_assert (nargs == expected_nargs);
 
--- gcc/testsuite/g++.dg/lookup/pr79377.C.jj    2017-02-06 17:41:22.316931623 
+0100
+++ gcc/testsuite/g++.dg/lookup/pr79377.C       2017-02-06 17:37:09.000000000 
+0100
@@ -0,0 +1,36 @@
+// PR c++/79377
+// { dg-do run }
+// { dg-options "-fpermissive" }
+
+struct A
+{
+  A () : a (0) {}
+  A& operator++ () { ++a; ++c; return *this; }
+  int a;
+  static int c;
+};
+
+int A::c = 0;
+
+template <typename>
+void
+foo (A& a)
+{
+  a++;         // { dg-warning "trying prefix operator instead" }
+  if (A::c != 3 || a.a != 3) __builtin_abort ();
+  ++a;
+  if (A::c != 4 || a.a != 4) __builtin_abort ();
+}
+
+int
+main ()
+{
+  A a;
+  if (A::c != 0 || a.a != 0) __builtin_abort ();
+  ++a;
+  if (A::c != 1 || a.a != 1) __builtin_abort ();
+  a++;         // { dg-warning "trying prefix operator instead" }
+  if (A::c != 2 || a.a != 2) __builtin_abort ();
+  foo<int> (a);
+  if (A::c != 4 || a.a != 4) __builtin_abort ();
+}

        Jakub