[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490 Marek Polacek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #8 from Marek Polacek --- Fixed in GCC 11.3 and 12.1.
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490
--- Comment #7 from CVS Commits ---
The releases/gcc-11 branch has been updated by Marek Polacek
:
https://gcc.gnu.org/g:5746f9199c2b8f0d679f13e3a48d6f8546a974f6
commit r11-9350-g5746f9199c2b8f0d679f13e3a48d6f8546a974f6
Author: Marek Polacek
Date: Sat Nov 6 18:10:39 2021 -0400
c++: Fix bogus error with __integer_pack [PR94490]
Here we issue a bogus:
error: '(0 ? fake_tuple_size_v : fake_tuple_size_v)' is not a
constant expression
because cxx_constant_value in expand_integer_pack gets
*(0 ? VIEW_CONVERT_EXPR(fake_tuple_size_v) :
VIEW_CONVERT_EXPR(fake_tuple_size_v))
which is a REFERENCE_REF_P and we evaluate its operand to 3, so we end
up with *3 and that fails. Sounds like we need to get rid of the
REFERENCE_REF_P then. That is what tsubst_copy_and_build/INDIRECT_REF
will do:
if (REFERENCE_REF_P (t))
{
/* A type conversion to reference type will be enclosed in
such an indirect ref, but the substitution of the cast
will have also added such an indirect ref. */
r = convert_from_reference (r);
}
so I think it's reasonable to call instantiate_non_dependent_expr_sfinae.
PR c++/94490
gcc/cp/ChangeLog:
* pt.c (expand_integer_pack): Call
instantiate_non_dependent_expr_sfinae.
gcc/testsuite/ChangeLog:
* g++.dg/ext/integer-pack5.C: New test.
(cherry picked from commit 9af081003f9c19f33457e0ed1aa14a764f462c3c)
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490
--- Comment #6 from CVS Commits ---
The trunk branch has been updated by Marek Polacek :
https://gcc.gnu.org/g:9af081003f9c19f33457e0ed1aa14a764f462c3c
commit r12-5712-g9af081003f9c19f33457e0ed1aa14a764f462c3c
Author: Marek Polacek
Date: Sat Nov 6 18:10:39 2021 -0400
c++: Fix bogus error with __integer_pack [PR94490]
Here we issue a bogus:
error: '(0 ? fake_tuple_size_v : fake_tuple_size_v)' is not a
constant expression
because cxx_constant_value in expand_integer_pack gets
*(0 ? VIEW_CONVERT_EXPR(fake_tuple_size_v) :
VIEW_CONVERT_EXPR(fake_tuple_size_v))
which is a REFERENCE_REF_P and we evaluate its operand to 3, so we end
up with *3 and that fails. Sounds like we need to get rid of the
REFERENCE_REF_P then. That is what tsubst_copy_and_build/INDIRECT_REF
will do:
if (REFERENCE_REF_P (t))
{
/* A type conversion to reference type will be enclosed in
such an indirect ref, but the substitution of the cast
will have also added such an indirect ref. */
r = convert_from_reference (r);
}
so I think it's reasonable to call instantiate_non_dependent_expr_sfinae.
PR c++/94490
gcc/cp/ChangeLog:
* pt.c (expand_integer_pack): Call
instantiate_non_dependent_expr_sfinae.
gcc/testsuite/ChangeLog:
* g++.dg/ext/integer-pack5.C: New test.
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490 --- Comment #5 from Marek Polacek --- Patch finally posted: https://gcc.gnu.org/pipermail/gcc-patches/2021-December/585932.html
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490 Marek Polacek changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org --- Comment #4 from Marek Polacek --- Nice, thanks. I'll take this one then; hopefully I'll get to it soon.
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490 Patrick Palka changed: What|Removed |Added Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed||2021-05-27 CC||ppalka at gcc dot gnu.org --- Comment #3 from Patrick Palka --- Marek, it looks like your https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94489#c2 patch also fixes this PR.
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490
ensadc at mailnesia dot com changed:
What|Removed |Added
CC||ensadc at mailnesia dot com
--- Comment #2 from ensadc at mailnesia dot com ---
reduced & modified:
```
template
constexpr int fake_tuple_size_v = 3;
template struct intseq {};
template using genseq = intseq<__integer_pack(N)...>;
template>
struct arith_result
{ };
template
auto Mul(const T&)
{
return [](auto) { return arith_result> { }; }(0);
}
auto x = Mul(0);
```
[Bug c++/94490] Ternary expression with 3 consts is “not” a constant expression
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94490 Marek Polacek changed: What|Removed |Added CC||mpolacek at gcc dot gnu.org --- Comment #1 from Marek Polacek --- In expand_integer_pack tsubst_copy_and_build produces *(0 ? tuple_size_v : tuple_size_v) and cxx_constant_value complains, because we turn tuple_size_v into '2' and so we're dereferencing an INTEGER_CST.
