Compiling source code for debugging, including: receiving, by an optimizing compiler from a debugger, a user specification of preferred breakpoint locations in the source code; compiling, by the optimizing compiler, the source code, wherein compiling includes inserting a snapshot at one or more of the preferred breakpoint locations, and recording the location of each inserted snapshot; and providing, to the debugger by the optimizing compiler, the recorded locations of each inserted snapshot along with the compiled source code.