https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121691
Bug ID: 121691
Summary: -Wcomma-within-single-parentheses: New diagnostic for
non-robust uses of the comma operator
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
The comma operator is easily confused with other uses of the comma token in C.
Within parenthesized expressions, it can be confused as a function argument
list separator, and if a function identifier is put before that parenthesized
expression, it can change the meaning significantly, possibly without a
diagnostic.
Since the comma operator is very rarely useful, it would be good to write code
that makes it explicit that it's a comma operator and cannot change meaning
easily.
For example, if I write a macro that uses the comma operator, I'd write it as
#define foo ((expr1, expr2, expr3))
If I put a function identifier before that, it will not transform into a
function call with 3 arguments, which makes it robust.
I'd like a diagnostic that complains about (expr1, expr2, expr3), so that it
forces me to add a second set of parentheses.
The behavior of this proposed diagnostic would be:
0, 0, 1; // ok
(0, 0, 1); // -Wcomma-within-single-parentheses
((0, 0, 1)); // ok
