1. A method, comprising: comparing a function associated with a computer program being executed to configuration data from a user created configuration file to determine whether the function is to be modified, the function specified within a callback sent from a runtime library, the configuration data identifying functions desired for modification; and responsive to determining that the function is to be modified: trapping the callback before delivery of the callback to a compiler associated with the computer program; injecting modifying intermediate language code from a file separate from the computer program into intermediate language code associated with the computer program to create modified intermediate language code, the modified intermediate language code comprising at least some of the intermediate language code and the modifying intermediate language code, the modified intermediate language code configured to perform a modified function when executed, the modified function comprising a modification of the function; modifying the callback with the modified intermediate language code to create a modified callback; and providing the modified callback, instead of the callback, to the compiler for compilation.