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* [Bug c++/101998] New: false positive: taking address of rvalue
@ 2021-08-20 14:35 peciva at fit dot vut.cz
2021-08-20 14:40 ` [Bug c++/101998] " redi at gcc dot gnu.org
2021-08-21 6:14 ` peciva at fit dot vut.cz
0 siblings, 2 replies; 3+ messages in thread
From: peciva at fit dot vut.cz @ 2021-08-20 14:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101998
Bug ID: 101998
Summary: false positive: taking address of rvalue
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: peciva at fit dot vut.cz
Target Milestone: ---
Following code refuses to compile (on g++ 7.5 and 11.2):
struct Nested {
int payload;
};
struct Main {
const Nested* nested;
int payload;
Main(const Nested* n) : nested(n) {}
};
void f(const Main& s)
{
}
int main() {
f(Main(&(const Nested&)Nested())); // <- workaround
f(Main(&Nested())); // <- fails here
return 0;
}
Error message: "error: taking address of rvalue"
I am not c++ expert, but the code seems perfectly meaningful to me. Structure
Main and Nested are both constructed before the call to f and both of them are
destructed after the execution of f. No dangling pointer to destructed
temporary. Both structures (Main, Nested) are temporaries and I do not see a
real reason why the compilation should fail. Maybe, if Main and Nested
instances are both temporaries, the error should not be emitted and compilation
shall proceed (?). But I am not expert.
Such constructions of temporary nested structures and passing pointers to main
structure constructor are often used when programming with c++ Vulkan API, for
instance.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/101998] false positive: taking address of rvalue
2021-08-20 14:35 [Bug c++/101998] New: false positive: taking address of rvalue peciva at fit dot vut.cz
@ 2021-08-20 14:40 ` redi at gcc dot gnu.org
2021-08-21 6:14 ` peciva at fit dot vut.cz
1 sibling, 0 replies; 3+ messages in thread
From: redi at gcc dot gnu.org @ 2021-08-20 14:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101998
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The C++ standard forbids it, that's why GCC gives an error.
"The operand of the unary & operator shall be an lvalue of some type T."
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/101998] false positive: taking address of rvalue
2021-08-20 14:35 [Bug c++/101998] New: false positive: taking address of rvalue peciva at fit dot vut.cz
2021-08-20 14:40 ` [Bug c++/101998] " redi at gcc dot gnu.org
@ 2021-08-21 6:14 ` peciva at fit dot vut.cz
1 sibling, 0 replies; 3+ messages in thread
From: peciva at fit dot vut.cz @ 2021-08-21 6:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101998
--- Comment #2 from Jan Pečiva <peciva at fit dot vut.cz> ---
I see. Thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-08-20 14:35 [Bug c++/101998] New: false positive: taking address of rvalue peciva at fit dot vut.cz
2021-08-20 14:40 ` [Bug c++/101998] " redi at gcc dot gnu.org
2021-08-21 6:14 ` peciva at fit dot vut.cz
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