Hi!
The following testcase is miscompiled. We see the constructor is immediate,
in build_over_call we trigger:
if (obj_arg && is_dummy_object (obj_arg))
{
call = build_cplus_new (DECL_CONTEXT (fndecl), call, complain);
obj_arg = NULL_TREE;
}
which makes call a TARGET_EXPR with the dtor in TARGET_EXPR_CLEANUP,
but then call cxx_constant_value on it. In cxx_eval_outermost_constant_expr
it triggers the:
else if (TREE_CODE (t) != CONSTRUCTOR)
{
r = get_target_expr_sfinae (r, tf_warning_or_error | tf_no_cleanup);
TREE_CONSTANT (r) = true;
}
which wraps the CONSTRUCTOR r into a new TARGET_EXPR, but one without
dtors (I think we need e.g. the TREE_CONSTANT for the callers),
and finally build_over_call uses that.
The following patch fixes that by reusing the earlier TARGET_EXPR and
overwriting TARGET_EXPR_INITIAL in it; I think the TARGET_EXPR_SLOT can't
appear in the TARGET_EXPR_INITIAL, because the CONSTRUCTOR has been built
already before get_target_expr_sfinae has been called and addresses of
an automatic var aren't constant expression.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-01-18 Jakub Jelinek <ja...@redhat.com>
PR c++/104055
* call.c (build_over_call): If in a call to consteval ctor call
is a TARGET_EXPR with cleanups and cxx_constant_value returns
a different TARGET_EXPR, reuse the original TARGET_EXPR with
the new TARGET_EXPR_INITIAL.
* g++.dg/cpp2a/consteval27.C: New test.
--- gcc/cp/call.c.jj 2022-01-11 23:11:22.049294946 +0100
+++ gcc/cp/call.c 2022-01-17 11:48:50.272044412 +0100
@@ -9935,7 +9935,14 @@ build_over_call (struct z_candidate *can
obj_arg = TREE_OPERAND (addr, 0);
}
}
- call = cxx_constant_value (call, obj_arg);
+ tree cst_call = cxx_constant_value (call, obj_arg);
+ if (call != cst_call
+ && TREE_CODE (call) == TARGET_EXPR
+ && TARGET_EXPR_CLEANUP (call)
+ && TREE_CODE (cst_call) == TARGET_EXPR)
+ TARGET_EXPR_INITIAL (call) = TARGET_EXPR_INITIAL (cst_call);
+ else
+ call = cst_call;
if (obj_arg && !error_operand_p (call))
call = build2 (INIT_EXPR, void_type_node, obj_arg, call);
call = convert_from_reference (call);
--- gcc/testsuite/g++.dg/cpp2a/consteval27.C.jj 2022-01-17 11:54:09.656459199
+0100
+++ gcc/testsuite/g++.dg/cpp2a/consteval27.C 2022-01-17 11:54:37.035068677
+0100
@@ -0,0 +1,18 @@
+// PR c++/104055
+// { dg-do run { target c++20 } }
+
+int g;
+
+struct A {
+ ~A () { if (a != 17 || b != 26) __builtin_abort (); g = 42; }
+ consteval A () : a (17), b (26) {}
+ int a, b;
+};
+
+int
+main ()
+{
+ A{};
+ if (g != 42)
+ __builtin_abort ();
+}
Jakub
