Re: Thread safety

=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <>
Wed, 06 Jun 2007 21:34:09 GMT
On 2007-06-06 22:57, wrote:

On Jun 6, 8:25 pm, Gianni Mariani <> wrote: wrote:

Are the following thread safe:

Assuming you're using either GCC, VC++ or the Intel compiler...

1. Assuming Object is any simple object
Object* fn()
   Object *p = new Object();
   return p;

Safe if you use the supplied new operator.

2. is return by value thread safe?

Safe if the copy constructor is thread safe.

3. int *p = new int
is this thread safe?

Safe assuming that p is not used before it is initialized.

Thanks for the reply... i just have 2 quick question:

1. You said that if i use the default new operator then using
Object *p = new Object();
is thread safe right...

but if i have a condition like:
Object1* p1 = new Object1();
else if(thread2)
Object2* p1 = new Object2();

and if both thread1 and thread2 are active at the same time and
running the above code then will new still be thread safe?

Since p1 is on the stack of the thread running (and thus local to the
thread) there should be no problem. On the other hand if p1 was a global
variable (and we assume that you can assign a pointer of both type
Object1* and type Object2*) then you would have a problem unless you
provide some mediation of access to p1.

Erik Wikstr?m

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