https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86201
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The problem here is that we report the missing return value:
9224 permerror (input_location, "return-statement with no value, in "
9225 "function returning %qT", valtype);
but permerror will end up calling print_instantiation_full_context, which ends
up calling dump_template_bindings and then tsubst -> tsubst_copy_and_build ->
build_functional_cast -> ... -> ocp_convert
which has (complain is tf_none)
829 if (complain & tf_warning)
830 return cp_truthvalue_conversion (e);
831 else
832 {
833 /* Prevent bogus -Wint-in-bool-context warnings coming
834 from c_common_truthvalue_conversion down the line. */
835 warning_sentinel w (warn_int_in_bool_context);
836 return cp_truthvalue_conversion (e);
837 }
So we call cp_truthvalue_conversion -> c_common_truthvalue_conversion ->
build_binary_op which only calls cp_build_binary_op but with
tf_warning_or_error. So even though the warning
4736 if ((complain & tf_warning)
4737 && (FLOAT_TYPE_P (type0) || FLOAT_TYPE_P (type1)))
4738 warning (OPT_Wfloat_equal,
4739 "comparing floating point with == or != is unsafe");
is properly guarded, we still re-enter the diagnostic routines.
