Gprof

Gprof is a performance analysis tool for profiling applications on Unix-like systems. It combines instrumentation with a call graph to help developers understand where a program spends its execution time. Gprof originated with the GNU Project and is commonly used with C, C++, and Fortran programs.

To collect data, the program must be compiled with the -pg option, and linked normally. At run time, instrumentation records entries and exits for functions, collects timing information, and maintains a call graph indicating which functions call which others and how often.

When execution finishes, a file named gmon.out is produced in the working directory. Running gprof with the executable and gmon.out generates a textual report that contains two main sections: a flat profile listing the time spent in each function, and a call graph showing the relationship and time spent in calls between functions.

The tool provides a straightforward view of hotspots and call relationships, useful for performance tuning and understanding program structure. Its main limitations include the overhead introduced by instrumentation, reduced accuracy for highly optimized code or multi-threaded programs, and the requirement to rebuild with -pg. The data reflects CPU time collected during the run and may not capture all behavior.

Gprof is part of the GNU Binutils suite and has been a standard profiling option on many Unix-like systems, though more modern profilers exist for certain workloads.