Mail Archives: cygwin/2006/03/22/07:55:59
On Mar 16 18:11, Samuel Thibault wrote:
> Hi,
>
> Jonathan Lennox, le Thu 16 Mar 2006 12:03:03 -0500, a écrit :
> Content-Description: message body text
> > In general, the idea of verifying objects on their init functions seems
> > dubious to me -- how can you tell initialized objects from random stack or
> > heap garbage?
>
> Posix says:
> Attempting to initialize an already initialized mutex results in undefined
> behavior.
According to SUSv3 pthread_mutex_init is allowed to check the incoming
mutex and return EBUSY if the mutex is already in use:
The pthread_mutex_init() function may fail if:
[EBUSY]
The implementation has detected an attempt to reinitialize the
object referenced by mutex, a previously initialized, but not yet
destroyed, mutex.
But the problem is obvious. On initializing an object you can't trust
the value on the stack to be meant as a pointer to an existing object,
or to be just random bytes or, in your nice example, being a value left
on the stack by an earlier function call. That's probably the reason
why SUSv3 says "may" and not "must", and that's probably also the reason
that such a test isn't made on Linux. I disabled the validity checks
now in the methods corresponding to the functions pthread_mutex_init,
pthread_rwlock_init and pthread_cond_init.
Thanks for the testcase, Jonathan.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
Red Hat
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