Thanks for the advice. There is one error in the
original code frag, though:
(taken from the Linux threads man
pages)
The sem_wait and sem_getvalue
functions always return 0.
So, the assert() on sem_getvalue() should always
have worked,
under the linux threads documentation.
pthreads-win32, however, seems to return -1
on failure (which
is ok for the code frag)
if ( result != 0 )
{
errno =
result;
return -1;
}
However, this indicates that the sem_getvalue() implementation in pthreads-win32, or my
compilation, is not quite as it should be.
Thanks to J Bossom for his suggestion. The
following fragment
compiles and runs just fine:
#include <semaphore.h>
#include
<cassert>
#include <iostream>
using namespace std;
int main()
{
/**
* We want to check wether a semaphore can be
initialised
* with a value.
*/
// a semaphore
sem_t
psem;
// initialise it with value
10
assert(sem_init(&psem,0,10) == 0);
// if
the semaphore initialisation was ok, the sem
// should now have
the value 10
// trying out J Bossom's idea of
counting down
// using a trywait
int
cnt=0;
while (sem_trywait(&psem)==0) cnt++;
cout << "Final value of cnt is " << cnt << endl <<
flush;
return 0;
}
This indicates that the sem_init() and
sem_trywait(), functions
are OK.