https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114104
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |ppalka at gcc dot gnu.org
--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Harald van Dijk from comment #2)
> For similar useless operations, such as f() ^ true;, GCC emits a similar
> warning "warning: value computed is not used [-Wunused-value]". Presumably,
> if that warning were implemented in GCC for ! as well, it should also fire
> for your original x != 0 test?
That sounds plausible. The relevant code is
gcc/cp/cvt.cc
@@ -1647,11 +1647,6 @@ convert_to_void (tree expr, impl_conv_void implicit,
tsubst_flags_t complain)
enum tree_code code = TREE_CODE (e);
enum tree_code_class tclass = TREE_CODE_CLASS (code);
if (tclass == tcc_comparison
|| tclass == tcc_unary
|| tclass == tcc_binary
|| code == VEC_PERM_EXPR
|| code == VEC_COND_EXPR)
warn_if_unused_value (e, loc);
which doesn't consider boolean operations (TRUTH_NOT_EXPR / TRUTH_AND_EXPR /
TRUTH_OR_EXPR) because their class is tcc_expression. This is probably just an
oversight (even the C front end warns for !f()).
