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* [Bug c++/96414] New: Second char relation test incorrect with constexpr dynamic allocation
@ 2020-08-02 0:13 pkeir at outlook dot com
2020-08-02 0:15 ` [Bug c++/96414] " pkeir at outlook dot com
2021-04-19 1:53 ` ppalka at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: pkeir at outlook dot com @ 2020-08-02 0:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96414
Bug ID: 96414
Summary: Second char relation test incorrect with constexpr
dynamic allocation
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: pkeir at outlook dot com
Target Milestone: ---
Created attachment 48981
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48981&action=edit
The file containing the code described.
The attached C++20 code behaves differently at compile-time than at runtime,
but shouldn't. As with `__gnu_cxx::char_traits<char>::lt`, the function
`lt_fun` applies built-in `operator<` to two character references, and returns
the result as an `int`. However, with the character pointer `pc` pointing to
memory allocated dynamically, the second call returns true (1) indicating that
'a' < 'a' is true. This is demonstrated by a failing static assert. Commenting
out the static assert produces an executable which correctly reports that 'a' <
'a' is false; by returning a 0.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/96414] Second char relation test incorrect with constexpr dynamic allocation
2020-08-02 0:13 [Bug c++/96414] New: Second char relation test incorrect with constexpr dynamic allocation pkeir at outlook dot com
@ 2020-08-02 0:15 ` pkeir at outlook dot com
2021-04-19 1:53 ` ppalka at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pkeir at outlook dot com @ 2020-08-02 0:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96414
--- Comment #1 from Paul Keir <pkeir at outlook dot com> ---
constexpr int lt_fun(const char& c1, const char& c2) {
return c1 < c2;
}
constexpr bool doit()
{
char *pc = new char;
const char* s = "a";
*pc = 'b';
lt_fun(*s, *pc); // a < b
*pc = 'a';
bool lt = lt_fun(*s, *pc); // a < a
delete pc;
return !lt;
}
int main(int argc, char *argv[])
{
static_assert(doit());
return doit() ? 0 : -1;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/96414] Second char relation test incorrect with constexpr dynamic allocation
2020-08-02 0:13 [Bug c++/96414] New: Second char relation test incorrect with constexpr dynamic allocation pkeir at outlook dot com
2020-08-02 0:15 ` [Bug c++/96414] " pkeir at outlook dot com
@ 2021-04-19 1:53 ` ppalka at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: ppalka at gcc dot gnu.org @ 2021-04-19 1:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96414
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
CC| |ppalka at gcc dot gnu.org
--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Thanks for the bug report. I think the underlying bug here is the same as that
of the recently fixed PR99859, and indeed trunk accepts your testcase ever
since r11-8056, so I'm going to mark this PR as a duplicate.
*** This bug has been marked as a duplicate of bug 99859 ***
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-08-02 0:13 [Bug c++/96414] New: Second char relation test incorrect with constexpr dynamic allocation pkeir at outlook dot com
2020-08-02 0:15 ` [Bug c++/96414] " pkeir at outlook dot com
2021-04-19 1:53 ` ppalka at gcc dot gnu.org
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