Looking at the differences between the patch I submitted for sem.c and
the original code, I figured out why the original code for unnamed
semaphores was crashing my otherwise posix correct use of semaphores.
The sem_init() function is returning the address of a new semaphore,
but this is not right. sem_init() initializes the semaphore *at* the
address pointed. To return the address of a new semaphore, sem_open()
is used.
Furthermore, from the man pages:
"Before being used, an unnamed semaphore must be initialized using
sem_init(3). It can then be operated on using
sem_post(3) and sem_wait(3).
When the semaphore is no longer required, and before
the memory in which it
is located is deallocated, the semaphore should
be destroyed using
sem_destroy(3)."
So in doubt, I go to the code in glibc, and find:
int
__new_sem_init (sem, pshared, value)
sem_t *sem;
int pshared;
unsigned int value;
{
/* Parameter sanity check. */
if (__builtin_expect (value > SEM_VALUE_MAX, 0))
{
__set_errno (EINVAL);
return -1;
}
/* Map to the internal type. */
struct new_sem *isem = (struct new_sem *) sem;
/* Use the values the user provided. */
isem->value = value;
#ifdef __ASSUME_PRIVATE_FUTEX
isem->private = pshared ? 0 : FUTEX_PRIVATE_FLAG;
#else
isem->private = pshared ? 0 : THREAD_GETMEM (THREAD_SELF,
header.private_futex);
#endif
isem->nwaiters = 0;
return 0;
}
Which means that the original code for semaphores in mingw-w64 is not
only incomplete (missing named semaphores) but broken.
The patch I submitted is missing a working sem_getvalue() function.
I'll prepare another patch with that function in working order and
some more changes on off-list suggestions by dw.
--
------------------------------------------------------------------------------------
Dr. Edscott Wilson Garcia
Applied Mathematics and Computing
Mexican Petroleum Institute
------------------------------------------------------------------------------
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