[Bug c++/91314] Confusing warning refers to nonexistent comma operator
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91314 Marek Polacek changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2019-08-21 CC||mpolacek at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #4 from Marek Polacek --- Confirmed. Probably comes from genericize_compound_lvalue.
[Bug c++/91314] Confusing warning refers to nonexistent comma operator
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91314
Eric Gallager changed:
What|Removed |Added
CC||egallager at gcc dot gnu.org
--- Comment #3 from Eric Gallager ---
(In reply to Keith Thompson from comment #0)
> Test case:
>
> int main() {
> int a;
> &(a=0);
> }
>
> Demonstration:
>
> $ g++ -c -Wunused-value confusing_warning.cpp
> confusing_warning.cpp: In function ‘int main()’:
> confusing_warning.cpp:3:7: warning: right operand of comma operator has no
> effect [-Wunused-value]
> 3 | &(a=0);
> | ^
>
> The problem: The warning refers to a comma operator that does not
> exist in the source.
Reminds me of bug 70619
>
> Speculation (please ignore this if it's not useful):
> The compiler internally generates some internal data structure that's
> similar to a comma operator (something like `(a=0), `) and the
> warning message is based on that.
>
> I've reproduced this problem with all versions of g++ I have access
> to, from 4.1.2 to 10.0.0 20190718 (experimental).
>
> This problem was originally reported by Stefan Ram
> on comp.lang.c++, 2019-07-24, thread "why can't I apply a bitwise modifier
> directly in a function call?".
[Bug c++/91314] Confusing warning refers to nonexistent comma operator
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91314 Harald van Dijk changed: What|Removed |Added CC||harald at gigawatt dot nl --- Comment #2 from Harald van Dijk --- (In reply to Keith Thompson from comment #0) > I've reproduced this problem with all versions of g++ I have access > to, from 4.1.2 to 10.0.0 20190718 (experimental). GCC has generated a warning for this since at least GCC 2, but up to 3.3, the warning was warning: value computed is not used which is correct. In GCC 3.4, the warning changed to warning: right-hand operand of comma has no effect
[Bug c++/91314] Confusing warning refers to nonexistent comma operator
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91314 --- Comment #1 from Keith Thompson --- Irrelevant correction: The post was in comp.lang.c, not comp.lang.c++.
