[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 Jakub Jelinek changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #11 from Jakub Jelinek --- Fixed.
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 --- Comment #10 from CVS Commits --- The releases/gcc-10 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:2513dad670c00dd9db3a85be348f6f4020b18b81 commit r10-8853-g2513dad670c00dd9db3a85be348f6f4020b18b81 Author: Jakub Jelinek Date: Thu Oct 1 11:18:35 2020 +0200 c++: Fix up default initialization with consteval default ctor [PR96994] > > The following testcase is miscompiled (in particular the a and i > > initialization). The problem is that build_special_member_call due to > > the immediate constructors (but not evaluated in constant expression mode) > > doesn't create a CALL_EXPR, but returns a TARGET_EXPR with CONSTRUCTOR > > as the initializer for it, > > That seems like the bug; at the end of build_over_call, after you > > >call = cxx_constant_value (call, obj_arg); > > You need to build an INIT_EXPR if obj_arg isn't a dummy. That works. obj_arg is NULL if it is a dummy from the earlier code. 2020-10-01 Jakub Jelinek PR c++/96994 * call.c (build_over_call): If obj_arg is non-NULL, return INIT_EXPR setting obj_arg to call. * g++.dg/cpp2a/consteval18.C: New test. (cherry picked from commit 56da736cc6ced0f1c339744321a14ae569db8606)
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 --- Comment #9 from CVS Commits --- The master branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:56da736cc6ced0f1c339744321a14ae569db8606 commit r11-3582-g56da736cc6ced0f1c339744321a14ae569db8606 Author: Jakub Jelinek Date: Thu Oct 1 11:18:35 2020 +0200 c++: Fix up default initialization with consteval default ctor [PR96994] > > The following testcase is miscompiled (in particular the a and i > > initialization). The problem is that build_special_member_call due to > > the immediate constructors (but not evaluated in constant expression mode) > > doesn't create a CALL_EXPR, but returns a TARGET_EXPR with CONSTRUCTOR > > as the initializer for it, > > That seems like the bug; at the end of build_over_call, after you > > >call = cxx_constant_value (call, obj_arg); > > You need to build an INIT_EXPR if obj_arg isn't a dummy. That works. obj_arg is NULL if it is a dummy from the earlier code. 2020-10-01 Jakub Jelinek PR c++/96994 * call.c (build_over_call): If obj_arg is non-NULL, return INIT_EXPR setting obj_arg to call. * g++.dg/cpp2a/consteval18.C: New test.
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 Marek Polacek changed: What|Removed |Added Keywords||patch --- Comment #8 from Marek Polacek --- Patch was posted: https://gcc.gnu.org/pipermail/gcc-patches/2020-September/553948.html
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 --- Comment #7 from Jakub Jelinek --- So, what I see is that expand_default_init calls build_special_member_call for the default ctor, but because the default ctor is an immediate method, it returns a TARGET_EXPR with CONSTRUCTOR as the initializer, rather than a call. expand_default_init doesn't return anything, just appends the rval as statement, but that doesn't really do anything. So, one way to fix this would be in expand_default_init check for rval being a TARGET with TREE_CONSTANT as the initializer and if it is that, build an INIT_EXPR like it e.g. does that for constexpr ctors. --- gcc/cp/init.c.jj2020-09-10 11:24:05.019805303 +0200 +++ gcc/cp/init.c 2020-09-14 15:06:59.467341241 +0200 @@ -1999,6 +1999,9 @@ expand_default_init (tree binfo, tree tr rval = build2 (INIT_EXPR, type, exp, e); } } + else if (TREE_CODE (rval) == TARGET_EXPR + && TREE_CONSTANT (TARGET_EXPR_INITIAL (rval))) +rval = build2 (INIT_EXPR, type, exp, rval); /* FIXME put back convert_to_void? */ if (TREE_SIDE_EFFECTS (rval)) fixes the testcase
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 --- Comment #6 from Jakub Jelinek --- Though, when the ctor is constexpr, it is constant initialized even without it, so probably the bug is somewhere else.
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994
--- Comment #5 from Jakub Jelinek ---
More complete testcase:
struct A { consteval A () { i = 1; } consteval A (int x) : i (x) {} int i = 0;
};
struct B { constexpr B () { i = 1; } constexpr B (int x) : i (x) {} int i = 0;
};
A const a;
constexpr A b;
B const c;
A const constinit d;
A const e = 2;
constexpr A f = 3;
B const g = 4;
A const constinit h = 5;
A i;
B j;
A k = 6;
B l = 7;
static_assert (b.i == 1 && f.i == 3);
int
main()
{
if (a.i != 1 || c.i != 1 || d.i != 1 || e.i != 2 || g.i != 4 || h.i != 5
|| i.i != 1 || j.i != 1 || k.i != 6 || l.i != 7)
__builtin_abort ();
}
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994
--- Comment #4 from Marek Polacek ---
Yes, a way to fix this would be to do the build_functional_cast in
check_initializer:
6892 else if (DECL_DECLARED_CONSTEXPR_P (decl)
6893|| (flags & LOOKUP_CONSTINIT))
6894 {
6895 /* Declared constexpr or constinit, but no suitable
initializer;
6896 massage init appropriately so we can pass it into
6897 store_init_value for the error. */
6898 if (CLASS_TYPE_P (type)
6899 && (!init || TREE_CODE (init) == TREE_LIST))
6900 {
6901 init = build_functional_cast (input_location, type,
6902 init, tf_none);
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994
--- Comment #3 from Jakub Jelinek ---
Though:
struct A { consteval A (int x) { i = x; } int i = 0; };
struct B { constexpr B (int x) { i = x; } int i = 0; };
A const a = 1;
constexpr A b = 2;
B const c = 3;
A constinit d = 4;
static_assert (b.i == 2);
int
main()
{
if (a.i != 1 || c.i != 3 || d.i != 4)
__builtin_abort ();
}
works fine, so the problem is maybe just with default construction for
consteval ctor.
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994
Jakub Jelinek changed:
What|Removed |Added
CC||jakub at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek ---
Testcase without includes:
struct A { consteval A () { i = 1; } int i = 0; };
struct B { constexpr B () { i = 1; } int i = 0; };
A const a;
constexpr A b;
B const c;
A constinit d;
static_assert (b.i == 1);
int
main()
{
if (a.i != 1 || c.i != 1 || d.i != 1)
__builtin_abort ();
}
I wonder if we shouldn't treat variables with consteval ctors like if
constinit, which as the testcase shows works fine.
[Bug c++/96994] Missing code from consteval constructor initializing const variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96994 Marek Polacek changed: What|Removed |Added Status|UNCONFIRMED |NEW CC||mpolacek at gcc dot gnu.org Last reconfirmed||2020-09-09 Keywords||wrong-code Ever confirmed|0 |1 --- Comment #1 from Marek Polacek --- Confirmed.
