[Bug c/68039] Incorrect unused-result warning

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68039

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Since op1 and op2 in that COND_EXPR are the same, we fold the conditional
expression to a COMPOUND_EXPR:
  return x ();, 0;
so the result of x () looks unused.

Same for C++.