[Bug c++/86201] ICE: Error reporting routines re-entered

[mpolacek at gcc dot gnu.org]

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.