In some instances the user may encounter an error while printing a shared variable. In most of the cases this is caused by GDB UPC's inability to read data from the running thread.

For example, if variable is declared as "shared int A[NTHREADS]" than GDB UPC command "p A" would fail if any of the threads is running. Use "interrupt" command in upc mode or "interrupt -a" otherwise to stop all threads.