[boost] BOOST_HAS_PTHREADS, BOOST_HAS_SCHED_YIELD tests in config_test not strict enough

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-04-07 17:42:09

I'm looking at the results of some new tests I added to smart_ptr: 
spinlock_try_test, yield_k_test, and I'm seeing failures on platforms that 
(in single threaded mode, i.e. without <threading>multi) advertise 
BOOST_HAS_PTHREADS (and BOOST_HAS_SCHED_YIELD) but in reality do one of:

1. provide stub implementations of pthread_mutex_*, failing a 
pthread_mutex_trylock test;

2. provide stubs and segfault on pthread_mutex_trylock;

3. fail to link because of missing pthread_mutex_trylock;

4. fail to link because of missing sched_yield.

This isn't particularly odd or surprising. But I think that config_test 
ought to fail on these platforms, for the same reason my tests fail. The 
reason the test passes is because boost_has_pthreads.ipp and 
boost_has_sched_yield.ipp are too permissive; the first one only tests 
pthread_mutex_* functions that are stubbed and appear to work, the second 
doesn't attempt to actually call sched_yield and - presumably - the linker 
discards the reference.

Does this make any sense? :-)