I added proc generate_tracefile in this patch
https://sourceware.org/ml/gdb-patches/2014-03/msg00591.html but
tfile.exp isn't skipped as changelog entry said:
* gdb.trace/tfile.exp: Skip the test if generate_tracefile
return 0.
it is a mistake I made at the last minute. Patch below fixed it.
gdb/testsuite:
2014-08-15 Yao Qi <yao@codesourcery.com>
* gdb.trace/tfile.exp: Return -1 if generate_tracefile returns
false.