check_format(struct magic_set *ms, struct magic *m)
{
	char *ptr;

	for (ptr = m->desc; *ptr; ptr++)
		if (*ptr == '%')
			break;
	if (*ptr == '\0') {
		/* No format string; ok */
		return 1;
	}

	assert(file_nformats == file_nnames);

	if (m->type >= file_nformats) {
		file_magwarn(ms, "Internal error inconsistency between "
		    "m->type and format strings");		
		return -1;
	}
	if (file_formats[m->type] == FILE_FMT_NONE) {
		file_magwarn(ms, "No format string for `%s' with description "
		    "`%s'", m->desc, file_names[m->type]);
		return -1;
	}

	ptr++;
	if (check_format_type(ptr, file_formats[m->type]) == -1) {
		/*
		 * TODO: this error message is unhelpful if the format
		 * string is not one character long
		 */
		file_magwarn(ms, "Printf format `%c' is not valid for type "
		    "`%s' in description `%s'", *ptr ? *ptr : '?',
		    file_names[m->type], m->desc);
		return -1;
	}
	
	for (; *ptr; ptr++) {
		if (*ptr == '%') {
			file_magwarn(ms,
			    "Too many format strings (should have at most one) "
			    "for `%s' with description `%s'",
			    file_names[m->type], m->desc);
			return -1;
		}
	}
	return 0;
}

Originally addressing errors in controlling program flow through indirect calls or jumps, this CWE has been deprecated and its concerns merged into more precise modern classifications.