https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119747
Bug ID: 119747
Summary: Request for clearer diagnostic when consecutive commas
appear in a function call
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: barry.revzin at gmail dot com
Target Milestone: ---
Here is a reduced example of a problem I just spent a while debugging:
template <class... Args>
void f(int, Args...) {
}
#define CALL_F(v, ...) f(v, __VA_OPT__(,) __VA_ARGS__)
int main() {
CALL_F(1, 2);
}
The diagnostic that I get on gcc trunk (so 15, and with c++26 so as to have
__VA_OPT__ support) is:
<source>: In function 'int main()':
<source>:6:40: error: expected primary-expression before ',' token
6 | #define CALL_F(v, ...) f(v, __VA_OPT__(,) __VA_ARGS__)
| ^
<source>:9:5: note: in expansion of macro 'CALL_F'
9 | CALL_F(1, 2);
| ^~~~~~
I couldn't make heads or tails of this diagnostic. And couldn't tell what was
wrong with the code either.
It wasn't until I preprocessed it that the issue became obvious. I'm doing
this:
int main() {
f(1, , 2);
}
And gcc is helpfully pointing me to the 2nd comma and saying that I need a
primary-expression before that. Which is true! But it would be a lot more
helpful if the diagnostic told me I had consecutive commas.
Even something like:
<source>:6:40: error: expected primary-expression before ',' token, received
two consecutive commas
would've meant I would have instantly found the issue.
