[Bug c++/107797] "warning right operand of comma operator has no effect" for expressions with no comma operator

[mpolacek at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107797

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The artificial COMPOUND_EXPR here comes from build_new_1:

  if (init_expr)
    rval = build2 (COMPOUND_EXPR, TREE_TYPE (rval), init_expr, rval);
  if (cookie_expr)
    rval = build2 (COMPOUND_EXPR, TREE_TYPE (rval), cookie_expr, rval);

I think a few years ago I experimented with TREE_NO_WARNING, but that didn't
work.  But now we have suppress_warning et al so I may give it another shot.