Re: Heap memory available (W32 console app in Visual C++)
I'm afraid you're requesting a feature, that none of modern general purpose
operating systems implement.
There is no implicit synchronization mechanism for data. Mutex ownership is
just a token. A program "knows" that this particular state should only be
accessed while holding this token. If a program refuses to cooperate and
simply messes with the state without acquiring the "token", then you're
screwed. If the protected state is limited only to your own process, then
you can use CRITICAL_SECTION, which is actually a lightweight mutex.
Global memory availability is not a protected resource. You can ask how much
memory is globally available, and the next microsecond it may be gone.
Moreover, this is different thing than your local virtual address space
availability. While your process address space can only be changed by your
process, there is no guarantee that an allocation request could be
satisfied; precisely beause you can't know global memory availability.
"CriCri" <bitwyse@leTIRETmaquis.net> wrote in message
news:48b59fb3$0$913$ba4acef3@news.orange.fr...
Hello Sven
SvenC a ?crit :
There is no concept of locking an object like G so that automatically
all code accessing that object is synchronized.
In my view that is a very fundamental and important design fault in
these OS.
The system should track attempts to access global (shared) objects and
verify that no process holding a mutex is currently accessing them
_before_ granting access to any other process - whether it has requested
a mutex or not (and then grant access when the mutex is released).
I appreciate that that could represent a significant overhead, but to
me it seems crucial. The current situation as descibed by Igor is
totally anarchic and renders the use of a critical section in many
circumstances completely pointless.
In actual fact, the system's global and shared resources and data are
simply not under any control at all.
Is there any point where your view of mutexes differs from what I
described?
Not really - only what I said above ;-)
Regards
Christophe
--
bitwyse [PGP KeyID 0xA79C8F2C]
Les conseils - c'est ce qu'on demande quand on conna?t d?j? la r?ponse
mais aurait pr?f?r? ne pas la savoir.
http://www.le-maquis.net