In a computer system that uses a "snapshot-at-the-beginning" garbage collector and in which write barrier code is generated for pointer write instructions in order to support the operation of the garbage collector, a static analysis of the computer program source code is performed prior to generating compiled code for the application and garbage collector in order to identify source code instructions that, at runtime, will perform initializing pointer writes as indicated by the fact that they overwrite memory locations that contain a predetermined pre-write value, such as NULL. The identified instructions are then compiled in a conventional manner, but no write barrier code is generated for them. Thus, at runtime, those instructions that perform initializing writes will incur no write barrier cost penalty.