This commit alone doesn't change anything in the real-world:
- configure.ac currently checks for clock_gettime() only
when using pthreads.
- CMakeLists.txt doesn't check for clock_gettime() on Windows.
So clock_gettime() wasn't used with MinGW-w64 before either.
clock_gettime() provides monotonic time and it's better than
gettimeofday() in this sense. But clock_gettime() is defined
in winpthreads, and liblzma or xz needs nothing else from
winpthreads. By avoiding clock_gettime(), we avoid the dependency on
libwinpthread-1.dll or the need to link against the static version.
As a bonus, GetTickCount64() and MinGW-w64's gettimeofday() can be
faster than clock_gettime(CLOCK_MONOTONIC, &tv). The resolution
is more than good enough for the progress indicator in xz.
This way, if xz is stopped the elapsed time and estimated time
remaining won't get confused by the amount of time spent in
the stopped state.
This raises SIGSTOP. It's not clear to me if this is the correct way.
POSIX and glibc docs say that SIGTSTP shouldn't stop the process if
it is orphaned but this commit doesn't attempt to handle that.
Search for SIGTSTP in section 2.4.3:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
Previously, if threading was enabled HAVE_DECL_CLOCK_MONOTONIC would always
be set to 0 or 1. However, this macro was needed in xz so if xz was not
built with threading and HAVE_DECL_CLOCK_MONOTONIC was not defined but
HAVE_CLOCK_GETTIME was, it caused a warning during build. Now,
HAVE_DECL_CLOCK_MONOTONIC has been renamed to HAVE_CLOCK_MONOTONIC and
will only be set if it is 1.
xz --flush-timeout=2000, old version:
1. xz is started. The next flush will happen after two seconds.
2. No input for one second.
3. A burst of a few kilobytes of input.
4. No input for one second.
5. Two seconds have passed and flushing starts.
The first second counted towards the flush-timeout even though
there was no pending data. This can cause flushing to occur more
often than needed.
xz --flush-timeout=2000, after this commit:
1. xz is started.
2. No input for one second.
3. A burst of a few kilobytes of input. The next flush will
happen after two seconds counted from the time when the
first bytes of the burst were read.
4. No input for one second.
5. No input for another second.
6. Two seconds have passed and flushing starts.
This switches units from microseconds to milliseconds.
New clock_gettime(CLOCK_MONOTONIC) will be used if available.
There is still a fallback to gettimeofday().
Lasse Collin