Hi!
The testcases in the patch are either miscompiled or ICE with checking,
because the defaulted operator== is synthetized too early (but only if
constexpr), when the corresponding class type is still incomplete type.
The problem is that at that point the bitfield FIELD_DECLs still have as
TREE_TYPE their underlying type rather than integral type with their
precision and when layout_class_type is called for the class soon after
that, it changes those types but the COMPONENT_REFs type stay the way
that they were during the operator== synthetize_method type and the
middle-end is then upset by the mismatch of types.
As what exact type will be given isn't just a one liner but quite long code
especially for over-sized bitfields, I think it is best to just not
synthetize the comparison operators so early (the defaulted_late_check
change) and call defaulted_late_check for them once again as soon as the
class is complete.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2021-09-28 Jakub Jelinek <ja...@redhat.com>
PR c++/102490
* method.c (defaulted_late_check): Don't synthetize constexpr
defaulted comparisons if context is still incomplete type.
(finish_struct_1): Call defaulted_late_check again for defaulted
comparisons.
* g++.dg/cpp2a/spaceship-eq11.C: New test.
* g++.dg/cpp2a/spaceship-eq12.C: New test.
--- gcc/cp/method.c.jj 2021-09-15 08:55:37.563497558 +0200
+++ gcc/cp/method.c 2021-09-27 13:48:12.139271830 +0200
@@ -3160,8 +3160,11 @@ defaulted_late_check (tree fn)
if (kind == sfk_comparison)
{
/* If the function was declared constexpr, check that the definition
- qualifies. Otherwise we can define the function lazily. */
- if (DECL_DECLARED_CONSTEXPR_P (fn) && !DECL_INITIAL (fn))
+ qualifies. Otherwise we can define the function lazily.
+ Don't do this if the class type is still incomplete. */
+ if (DECL_DECLARED_CONSTEXPR_P (fn)
+ && !DECL_INITIAL (fn)
+ && COMPLETE_TYPE_P (ctx))
{
/* Prevent GC. */
function_depth++;
--- gcc/cp/class.c.jj 2021-09-03 09:46:28.801428380 +0200
+++ gcc/cp/class.c 2021-09-27 14:07:03.465562255 +0200
@@ -7467,7 +7467,14 @@ finish_struct_1 (tree t)
for any static member objects of the type we're working on. */
for (x = TYPE_FIELDS (t); x; x = DECL_CHAIN (x))
if (DECL_DECLARES_FUNCTION_P (x))
- DECL_IN_AGGR_P (x) = false;
+ {
+ /* Synthetize constexpr defaulted comparisons. */
+ if (!DECL_ARTIFICIAL (x)
+ && DECL_DEFAULTED_IN_CLASS_P (x)
+ && special_function_p (x) == sfk_comparison)
+ defaulted_late_check (x);
+ DECL_IN_AGGR_P (x) = false;
+ }
else if (VAR_P (x) && TREE_STATIC (x)
&& TREE_TYPE (x) != error_mark_node
&& same_type_p (TYPE_MAIN_VARIANT (TREE_TYPE (x)), t))
--- gcc/testsuite/g++.dg/cpp2a/spaceship-eq11.C.jj 2021-09-27
14:20:04.723713371 +0200
+++ gcc/testsuite/g++.dg/cpp2a/spaceship-eq11.C 2021-09-27 14:20:20.387495858
+0200
@@ -0,0 +1,43 @@
+// PR c++/102490
+// { dg-do run { target c++20 } }
+
+struct A
+{
+ unsigned char a : 1;
+ unsigned char b : 1;
+ constexpr bool operator== (const A &) const = default;
+};
+
+struct B
+{
+ unsigned char a : 8;
+ int : 0;
+ unsigned char b : 7;
+ constexpr bool operator== (const B &) const = default;
+};
+
+struct C
+{
+ unsigned char a : 3;
+ unsigned char b : 1;
+ constexpr bool operator== (const C &) const = default;
+};
+
+void
+foo (C &x, int y)
+{
+ x.b = y;
+}
+
+int
+main ()
+{
+ A a{}, b{};
+ B c{}, d{};
+ C e{}, f{};
+ a.b = 1;
+ d.b = 1;
+ foo (e, 0);
+ foo (f, 1);
+ return a == b || c == d || e == f;
+}
--- gcc/testsuite/g++.dg/cpp2a/spaceship-eq12.C.jj 2021-09-27
14:20:12.050611625 +0200
+++ gcc/testsuite/g++.dg/cpp2a/spaceship-eq12.C 2021-09-27 14:20:39.633228602
+0200
@@ -0,0 +1,5 @@
+// PR c++/102490
+// { dg-do run { target c++20 } }
+// { dg-options "-O2" }
+
+#include "spaceship-eq11.C"
Jakub
