Here is my proposal for changing the method trailer in order to be able to encode various stuff to trailer. Any corrections, suggestions are welcome. The kind of compiled method trailer is determined by the last byte of compiled method. The format is following: "2rkkkkkkdd" where 'k' bits stands for 'kind' , allowing totally 2^6 different kinds of method trailer and 'd' bits is data. The following is description of defined trailer kinds: k = 000000, dd = 00 method has no trailer, and total trailer size bytes is 1 (just for last byte) k = 000001, method has cleared trailer (it was set to something else, but then cleared) dd+1 determines the number of bytes for size field, and size is a total length of trailer bytes So a total length of trailer is: 1 + (dd + 1) + size k = 000010 the trailer contains a list of method temp names, compressed using qCompress: method. dd+1 determines the number of bytes for size field, and size is a number of bytes of compressed buffer. So a total length of trailer is: 1 + (dd + 1) + size k = 000011 the trailer contains a list of method temp names, compressed using GZIP compression method. dd+1 determines the number of bytes for size field, and size is a number of bytes of compressed buffer So a total length of trailer is: 1 + (dd + 1) + size k = 000100 the trailer indicates , that method source is determined by a class + selector where it is installed to. Trailer size = 1. k = 000101 the trailer indicates , that method source is determined by a class + some ByteString identifier. dd+1 determines the number of bytes for size field, denoting the length of ByteString identifier. A total length of trailer is: 1 + (dd + 1) + size k = 000110 the trailer contains an utf-8 encoded method source code, compressed using qCompress: method. dd+1 determines the number of bytes for size field, denoting the length of compressed buffer A total length of trailer is: 1 + (dd + 1) + size k = 000111 the trailer contains an utf-8 encoded method source code, comressed using GZIP dd+1 determines the number of bytes for size field, denoting the length of compressed buffer A total length of trailer is: 1 + (dd + 1) + size k = 111111 the trailer is encoded source pointer. Total trailer size is 4-bytes (this is backwards compatible with most of currently existing compiled methods) k = 111110 the trailer is encoded source pointer. Total trailer size is 5-bytes k = 111101 the trailer is encoded source pointer. Total trailer size is 6-bytes k = 111100 the trailer is encoded source pointer. Total trailer size is 7-bytes k = 111011 the trailer is encoded source pointer. Total trailer size is 8-bytes -- Best regards, Igor Stasenko AKA sig.