-bool fmt_check (const struct fmt_spec *, enum fmt_use);
-bool fmt_check_input (const struct fmt_spec *);
-bool fmt_check_output (const struct fmt_spec *);
-bool fmt_check_type_compat (const struct fmt_spec *, enum val_type);
-bool fmt_check_width_compat (const struct fmt_spec *, int var_width);
+bool fmt_check (struct fmt_spec, enum fmt_use);
+bool fmt_check_input (struct fmt_spec);
+bool fmt_check_output (struct fmt_spec);
+bool fmt_check_type_compat (struct fmt_spec, enum val_type);
+bool fmt_check_width_compat (struct fmt_spec, int var_width);
+
+char *fmt_check__ (struct fmt_spec, enum fmt_use);
+char *fmt_check_input__ (struct fmt_spec);
+char *fmt_check_output__ (struct fmt_spec);
+char *fmt_check_type_compat__ (struct fmt_spec, const char *varname,
+ enum val_type);
+char *fmt_check_width_compat__ (struct fmt_spec, const char *varname,
+ int var_width);