Instant crashing after replacing calls to clock() with MPI_Wtime()

Question

I have an MPI program that I'm developing on a local computer, but need to run on a remote machine. I used clock() to measure time, but after discovering that it doesn't work well enough on the remote machine (due to a completely different architecture), I replaced a few calls to clock() with MPI_Wtime(), which yielded the required results. The program still runs on both the local and remote machines.

However, I just went and replaced all the other calls to clock() with MPI_Wtime(), and now launching the program on the local machine immediately causes the processes to stop with exit code -1073741819. Even if I put a cout in the very first line of main(), there's no output, so I'm fairly sure it's not a programming fault on my part, but I have no idea what's wrong.

How can changes in the source code cause a program to fail before the changed code (or any code, for that matter) is executed?

Answer 1

Was that cout flushed by an 'endl' or 'flush' manipulator? If not, the program may have crashed afterwards but you'd never know because the buffered output would be lost.

Answer 2

Are you calling MPI_Wtime() from the constructor of a static object? These run before main().