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* [Bug c++/113713] New: static_assert result depends on optimization settings
@ 2024-02-02 8:08 fchelnokov at gmail dot com
2024-02-02 8:17 ` [Bug c++/113713] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: fchelnokov at gmail dot com @ 2024-02-02 8:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113713
Bug ID: 113713
Summary: static_assert result depends on optimization settings
Product: gcc
Version: 13.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fchelnokov at gmail dot com
Target Milestone: ---
This program
struct A{};
constexpr bool p(auto) { return false; }
constexpr bool f(auto v) { return p(v); }
constexpr bool g() { return f(A()); }
constexpr bool p(A) { return true; }
static_assert( f(A{}) );
The static_assert passes in GCC only with -O0 command line option, and it fails
with -O1 and higher optimization options, which looks wrong. Online demo:
https://godbolt.org/z/vWq8G7rn4
Related discussion: https://stackoverflow.com/q/77923182/7325599
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/113713] static_assert result depends on optimization settings
2024-02-02 8:08 [Bug c++/113713] New: static_assert result depends on optimization settings fchelnokov at gmail dot com
@ 2024-02-02 8:17 ` pinskia at gcc dot gnu.org
2024-02-02 8:28 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-02-02 8:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113713
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
C++11 testcase so it is easier to test against older versions of GCC:
```
struct A{};
template<class T>
constexpr bool p(T) { return false; }
template<class T>
constexpr bool f(T v) { return p(v); }
constexpr bool g() { return f(A()); }
constexpr bool p(A) { return true; }
void ff() {
static_assert( f(A{}) , "");
}
```
GCC 6 and before causes the static_assert to always to fail at all
optimizations level. GCC 7 and afterwards has the current behavior of true for
-O0 and false for -O1 and above.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/113713] static_assert result depends on optimization settings
2024-02-02 8:08 [Bug c++/113713] New: static_assert result depends on optimization settings fchelnokov at gmail dot com
2024-02-02 8:17 ` [Bug c++/113713] " pinskia at gcc dot gnu.org
@ 2024-02-02 8:28 ` pinskia at gcc dot gnu.org
2024-02-02 8:34 ` [Bug c++/113713] constexpr function values (incorrectly?) depend on optimization level pinskia at gcc dot gnu.org
2024-02-02 15:11 ` mpolacek at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-02-02 8:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113713
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2024-02-02
Status|UNCONFIRMED |NEW
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, this is a constexpr issue in both clang and GCC (unless there is
some unspecified behavior I don't know of).
Take:
```
#if defined(CE)
#define CONSTEXPR constexpr
#else
#define CONSTEXPR
#endif
struct A{};
template<class T>
CONSTEXPR
bool p(T) { return false; }
template<class T>
CONSTEXPR
bool f(T v) { return p(v); }
CONSTEXPR
bool g() { return f(A()); }
CONSTEXPR
bool p(A) { return true; }
int main()
{
A a;
if (!f(a))
__builtin_abort();
}
```
Without CE being defined, this works at all optimizations level. With CE being
defined this works at -O0 only (like there is some [incorrect?] caching going
on at -O1 and above and clang is doing the caching at all levels).
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/113713] constexpr function values (incorrectly?) depend on optimization level
2024-02-02 8:08 [Bug c++/113713] New: static_assert result depends on optimization settings fchelnokov at gmail dot com
2024-02-02 8:17 ` [Bug c++/113713] " pinskia at gcc dot gnu.org
2024-02-02 8:28 ` pinskia at gcc dot gnu.org
@ 2024-02-02 8:34 ` pinskia at gcc dot gnu.org
2024-02-02 15:11 ` mpolacek at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-02-02 8:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113713
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://gcc.gnu.org/pipermail/gcc-patches/2016-April/446612.html might be
related to the whole caching situtation but I could be wrong.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/113713] constexpr function values (incorrectly?) depend on optimization level
2024-02-02 8:08 [Bug c++/113713] New: static_assert result depends on optimization settings fchelnokov at gmail dot com
` (2 preceding siblings ...)
2024-02-02 8:34 ` [Bug c++/113713] constexpr function values (incorrectly?) depend on optimization level pinskia at gcc dot gnu.org
@ 2024-02-02 15:11 ` mpolacek at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2024-02-02 15:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113713
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mpolacek at gcc dot gnu.org
--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Looks like this changed with r11-4230-g46fdced6a9f936
commit 46fdced6a9f936ae4d5b42347d7d87f69875683a
Author: Patrick Palka <ppalka@redhat.com>
Date: Thu Oct 22 07:33:58 2020 -0400
c++: constexpr evaluation and bare EMPTY_CLASS_EXPR [PR96575]
but only when A is an empty class.
Using struct A { int i; };, the test has compiled with -O0 since
r7-4458-gf065303fcf9aa2.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-02-02 15:11 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2024-02-02 8:08 [Bug c++/113713] New: static_assert result depends on optimization settings fchelnokov at gmail dot com
2024-02-02 8:17 ` [Bug c++/113713] " pinskia at gcc dot gnu.org
2024-02-02 8:28 ` pinskia at gcc dot gnu.org
2024-02-02 8:34 ` [Bug c++/113713] constexpr function values (incorrectly?) depend on optimization level pinskia at gcc dot gnu.org
2024-02-02 15:11 ` mpolacek at gcc dot gnu.org
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