I'm using gperftools v2.3rc and would like to use the improved profiling of threads feature. The release notes state in part:
new cpu profiling mode on Linux is now implemented. It sets up separate profiling timers for separate threads. ... [It] is enabled if both librt.f is loaded and CPUPROFILE_PER_THREAD_TIMERS environment variable is set. ...
My C++ application is linked with librt.so (-lrt — the POSIX.1b Realtime Extensions library), but I have not heard of a library with a .f suffix before. What does the .f mean, where can I find this library, and how do I load it in my application?