Thanks to Hui and Jan for catching these!  Tested with a 
manually-corrupted trace file, and committed to trunk.

Stan

2010-01-16  Stan Shebs  <stan@codesourcery.com>

        * tracepoint.h (struct trace_status): Use unsigned long long
        instead of size_t.
        * tracepoint.c (trace_status_command): Fix printf directive.
        (trace_save_command): Check fwrite returns, fix printf directive.
        (trace_filename): New global.
        (tfile_open): Set it, check read returns.
        (tfile_close): Free trace_filename.
        (tfile_get_traceframe_address): Check read returns.
        (tfile_trace_find): Ditto.
        (tfile_fetch_registers): Ditto.
        (tfile_xfer_partial): Ditto.
        (tfile_get_trace_state_variable_value): Ditto.