// Replace all instance of calling of egl_*() function with the following block: { // local static that control and if the special diag code will be call. static struct { int control; int value; char* file=__FILE__; int line=__LINE__; } oCtrl; if (oCtrl->control==NOT_REGISTER) my_diag_register(oCtrl); else if (oCtrl->control==LOG_DIAG) my_diag_call(oCtrl); egl_*(....) // call the same function usb_*() function } With this, I like to dynamically turn on/off the call to my_diag_call() at run time. If it is possible, is there any similar "code transformation" .py script I can follow to figure out how to do this myself? Thanks -Tony p.s. On a related note, I love to see a sample gcc-plugin .py script that wrap C function() call with profiling code that collect call count and call duration with rdtsc, etc.