Closing my HDF5 file, I get a segfault with an error "MPI_FILE_SET_SIZE(76): Inconsistent arguments to collective routine"

This indicates that you have created datasets or groups or attributes in the file "uncollectively", meaning either not all processes called the create, or the creation was done with different parameters.

For example, a common mistake is to create a dataset with chunk dimensions (using H5Pset_chunk) that are not the same on all processes. Mistakes like that result in a different size of the file on all the processes and hence the MPI_File_set_size fails with different arguments between all the ranks.