https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126897
Bug ID: 126897
Summary: [constracts] Postconditions incorrectly treat
parameters in the left operand of a comma expression
as ODR-used.
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: c++-contracts, c++26, rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: zheng.xianyuwang at gmail dot com
Target Milestone: ---
Consider the following example:
```
void f (bool b)
post ((b, true))
{}
```
In the comma expression `(b, true)', the left operand `b' is a discarded-value
expression. Since a has non-volatile scalar type, no lvalue-to-rvalue
conversion is applied to it, so this use does not constitute an ODR-use.
Similar to the example in https://eel.is/c++draft/basic.def.odr#5.2.2.2:
```
int x, y;
int _ = ((cond ? x : y), 0); // does not odr-use x or y
```
