What are the possible side effects of using the GCC profile flag -pg?

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There is a device driver for a camera device provided to us as a .so library file by the vendor. Only the header file with API's is available which provides the list of functions that we can work with the device. Our application is linked with the .so library file provided by the vendor and uses the interface functions provided for our objective.

When we wanted to measure the time taken by our application in handling different tasks, we have added GCC -pg flag and compiled+built our application.

But we found that using this executable built with -pg, we are observing random failure in the camera image acquire functions. Since we are using the .so library file, we do not know what is going wrong inside that function.

So in general I wanted to understand what could be the possible reasons of such a failure mode. Any pointers or documents that can help what goes inside profiling and its side effects is appreciated.


This answer is a helpful overview of how the gcc -pg flag profiler actually works. The take-home point is mostly to do with possible changes to timing. If your library has any kind of time-sensitivity in it, introducing profiler overheads might be changing the time it takes to execute parts of the code, and perhaps violating some kind of constraint.