Fix build when RUSAGE_THREAD is not available & add warning
Building current GDB on Cygwin, fails like so:
/home/pedro/gdb/src/gdbsupport/run-time-clock.cc: In function ‘void get_run_time(user_cpu_time_clock::time_point&, system_cpu_time_clock::time_point&, run_time_scope ’:
/home/pedro/gdb/src/gdbsupport/run-time-clock.cc:52:13: error: ‘RUSAGE_THREAD’ was not declared in this scope; did you mean ‘SIGEV_THREAD’?
52 | who = RUSAGE_THREAD;
| ^~~~~~~~~~~~~
| SIGEV_THREAD
Cygwin does not implement RUSAGE_THREAD. Googling around, I see
Cygwin is not alone, other platforms don't support it either. For
example, here is someone suggesting an alternative for darwin/macos:
https://stackoverflow.com/questions/
5652463/equivalent-to-rusage-thread-darwin
Fix this by falling back to process scope if thread scope can't be
supported. I chose this instead of returning zero usage or some other
constant, because if gdb is built without threading support, then
process-scope run time usage is the right info to return.
But instead of falling back silently, print a warning (just once),
like so:
(gdb) maint set per-command time on
⚠️ warning: per-thread run time information not available on this platform
... so that developers on other platforms at least have a hint
upfront.
This new warning also shows on platforms that don't have getrusage in
the first place, but does not show if the build doesn't support
threading at all.
New tests are added to gdb.base/maint.exp, to expect the warning, and
also to ensure other "mt per-command" sub commands don't trigger the
new warning.
Change-Id: Ie01b916b62f87006f855e31594a5ac7cf09e4c02
Approved-By: Simon Marchi <simon.marchi@efficios.com>
Approved-By: Tom Tromey <tom@tromey.com>