An api for runtime code patching

The authors present a postcompiler program manipulation tool called Dyninst , which provides a C++ class library for program instrumentation. Using thi s library, it is possible to instrument and modify application programs dur ing execution. A unique feature of this library is that it permits machine- independent binary instrumentation programs to be written. The authors desc ribe the interface that a tool sees when using this library. They also disc uss three simple tools built using this interface: a utility to count the n umber of times a function is called, a program to capture the output of an already running program to a file, and an implementation of conditional bre akpoints. For the conditional breakpoint example, the authors show that by using their interface compared with gdb, they are able to execute a program with conditional breakpoints up to 900 times faster.