Free the stack for the thread

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1

Hi there,

I have used beginthread() in my driver to create a thread and I allocate the
stack in my program instead of letting the system to allocate the stack. The
reason is that I want to be able to free the stack evertime the thread end
so I had the program like the folllowing:

main()
{
char *args[2];

args[0]=(char *)malloc(STACK_SIZE);
_beginthrad(child,args[0],STACK_SIZE,args);
…
…
}

child(void far *parm)
{
char * stack =parm[0];
…
…
free(stack);
_endthread();
}

So my question is that can I free the stack before calling _endthared()? I
have run the program for some stress test, and so far, it doesn’t seem has
any problem, but I am still wondering is there any good suggestion for the
stack free up.

Thanks in advance!
Teresa

2

Teresa Tao <ttao@neontech.com> wrote:

Hi there,

I have used beginthread() in my driver to create a thread and I allocate the
stack in my program instead of letting the system to allocate the stack. The
reason is that I want to be able to free the stack evertime the thread end
so I had the program like the folllowing:

main()
{
char *args[2];

args[0]=(char *)malloc(STACK_SIZE);
_beginthrad(child,args[0],STACK_SIZE,args);
.
.
}

child(void far *parm)
{
char * stack =parm[0];
.
.
free(stack);
_endthread();
}

So my question is that can I free the stack before calling _endthared()? I
have run the program for some stress test, and so far, it doesn’t seem has
any problem, but I am still wondering is there any good suggestion for the
stack free up.

The question is, does _endthread(), or the act of calling _endthread()
write anything to the stack? If so, this is dangerous in that if you
get pre-empted after free() by another thread that calls malloc(), it
could get the memory you just freed, and then you would over-write its
new memory with whatever hit the stack in calling/inside _endthread().

I’d say the answer is that no, this isn’t safe.

-David