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* [Bug c++/108759] New: "mandatory copy elision" not implemented during constant evaluation redux
@ 2023-02-11 5:49 herring at lanl dot gov
2023-02-13 17:20 ` [Bug c++/108759] " mpolacek at gcc dot gnu.org
2023-04-27 17:39 ` arthur.j.odwyer at gmail dot com
0 siblings, 2 replies; 3+ messages in thread
From: herring at lanl dot gov @ 2023-02-11 5:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108759
Bug ID: 108759
Summary: "mandatory copy elision" not implemented during
constant evaluation redux
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: herring at lanl dot gov
Target Milestone: ---
Extending the test case in (the invalid) #94537 to have a user-provided
destructor does not cause the "mandatory copy elision" to take place even
though the implementation is no longer permitted to introduce a temporary:
struct A;
extern const A a;
struct A {
bool special=this==&a;
constexpr ~A() {}
};
constexpr A get() {return {};} // or "return A();"
constexpr A a=get();
static_assert(a.special);
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/108759] "mandatory copy elision" not implemented during constant evaluation redux
2023-02-11 5:49 [Bug c++/108759] New: "mandatory copy elision" not implemented during constant evaluation redux herring at lanl dot gov
@ 2023-02-13 17:20 ` mpolacek at gcc dot gnu.org
2023-04-27 17:39 ` arthur.j.odwyer at gmail dot com
1 sibling, 0 replies; 3+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2023-02-13 17:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108759
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-02-13
Status|UNCONFIRMED |NEW
CC| |mpolacek at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed, we haven't elided the TARGET_EXPR:
*<retval> = TARGET_EXPR <D.2533, {.special=(const struct A *)
&<PLACEHOLDER_EXPR struct A> == &a}>
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/108759] "mandatory copy elision" not implemented during constant evaluation redux
2023-02-11 5:49 [Bug c++/108759] New: "mandatory copy elision" not implemented during constant evaluation redux herring at lanl dot gov
2023-02-13 17:20 ` [Bug c++/108759] " mpolacek at gcc dot gnu.org
@ 2023-04-27 17:39 ` arthur.j.odwyer at gmail dot com
1 sibling, 0 replies; 3+ messages in thread
From: arthur.j.odwyer at gmail dot com @ 2023-04-27 17:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108759
Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |arthur.j.odwyer at gmail dot com
--- Comment #2 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> ---
I believe what I'm going to say is simply a duplicate of Davis's report, but
just in case it's different, I'll add mine here. This is a slightly modified
version of the example from [class.copy.elision], merely modified so that g()
returns a C++17 prvalue instead of relying on NRVO/copy-elision.
Original example: https://eel.is/c++draft/class.copy.elision#2
Modified example:
// https://godbolt.org/z/n43jPs1Kj
struct A {
void *p;
constexpr A(): p(this) {}
};
constexpr A g() {
return A();
}
constexpr A b = g(); // well-formed, b.p points to b
static_assert(b.p == &b);
MSVC and Clang accept. GCC incorrectly rejects:
<source>:11:19: error: 'A{((void*)(&<anonymous>))}' is not a constant
expression
11 | constexpr A b = g(); // well-formed, b.p points to b
| ^
<source>:12:19: error: non-constant condition for static assertion
12 | static_assert(b.p == &b);
| ~~~~^~~~~
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-04-27 17:39 UTC | newest]
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2023-02-11 5:49 [Bug c++/108759] New: "mandatory copy elision" not implemented during constant evaluation redux herring at lanl dot gov
2023-02-13 17:20 ` [Bug c++/108759] " mpolacek at gcc dot gnu.org
2023-04-27 17:39 ` arthur.j.odwyer at gmail dot com
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