static int spl_filesystem_file_read(spl_filesystem_object *intern, int silent TSRMLS_DC) /* {{{ */
{
	char *buf;
	size_t line_len = 0;
	long line_add = (intern->u.file.current_line || intern->u.file.current_zval) ? 1 : 0;

	spl_filesystem_file_free_line(intern TSRMLS_CC);
	
	if (php_stream_eof(intern->u.file.stream)) {
		if (!silent) {
			zend_throw_exception_ex(spl_ce_RuntimeException, 0 TSRMLS_CC, "Cannot read from file %s", intern->file_name);
		}
		return FAILURE;
	}

	if (intern->u.file.max_line_len > 0) {
		buf = safe_emalloc((intern->u.file.max_line_len + 1), sizeof(char), 0);
		if (php_stream_get_line(intern->u.file.stream, buf, intern->u.file.max_line_len + 1, &line_len) == NULL) {
			efree(buf);
			buf = NULL;
		} else {
			buf[line_len] = '\0';
		}
	} else {
		buf = php_stream_get_line(intern->u.file.stream, NULL, 0, &line_len);
	}

	if (!buf) {
		intern->u.file.current_line = estrdup("");
		intern->u.file.current_line_len = 0;
	} else {
		if (SPL_HAS_FLAG(intern->flags, SPL_FILE_OBJECT_DROP_NEW_LINE)) {
			line_len = strcspn(buf, "\r\n");
			buf[line_len] = '\0';
		}
	
		intern->u.file.current_line = buf;
		intern->u.file.current_line_len = line_len;
	}
	intern->u.file.current_line_num += line_add;

	return SUCCESS;
} /* }}} */
The software performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control.