Build farm animals running ancient HPUX and Solaris have a non-standard
sigwait() from draft versions of POSIX, so they didn't like commit
7c09d279. To avoid the problem in general, only try to use sigwait() if
it's declared by <signal.h> and matches the expected declaration. To
select the modern declaration on Solaris (even in non-threaded
programs), move -D_POSIX_PTHREAD_SEMANTICS into the right place to
affect all translation units.
Also fix the error checking. Modern sigwait() doesn't set errno.
Thanks to Tom Lane for help with this.
Discussion: https://postgr.es/m/3187588.1626136248%40sss.pgh.pa.us
Theoretically one could go into src/test/thread and build/run this
program there. In practice, that hasn't worked since 96bf88d52,
and probably much longer on some platforms (likely including just
the sort of hoary leftovers where this test might be of interest).
While it wouldn't be too hard to repair the breakage, the fact that
nobody has noticed for two years shows that there is zero usefulness
in maintaining this build pathway. Let's get rid of it and decree
that thread_test.c is *only* meant to be built/used in configure.
Given that decision, it makes sense to put thread_test.c under config/
and get rid of src/test/thread altogether, so that's what I did.
In passing, update src/test/README, which had been ignored by some
not-so-recent additions of subdirectories.
Discussion: https://postgr.es/m/227659.1603041612@sss.pgh.pa.us
Thomas Munro
Bruce Momjian
Tom Lane