Different instances of my class uses the same buffer????

[tonnot]

I have this class , I show you the constructor:

W_stream::W_stream{
  char mybuffer [265536];
  the_stream = new stringstream ;
  the_stream->rdbuf()->pubsetbuf(mybuffer,265536);
}

W_stream::W_stream{
  char mybuffer [265536];
  the_stream = new stringstream ;
  the_stream->rdbuf()->pubsetbuf(mybuffer,265536);
}

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This class has put and get methods to write and read data and has a int loc; to tell me the localization of internal pointer.

Ok, I create 2 instances:
my_wstream1= new W_stream();
my_wstream2= new W_stream();

And I use my_wstream1.put(a short int) 234 times and my_wstream2.put(a short int) 745.

Later my_wstream1 has loc of 234*4 and 745*4. Up to here all is right.

But later my_wstream1.get gives me values that it be supossed has been written by my_wstream2 ????

The question is mybuffer are the same ?? I dont understand ???
Mybuffer is private to W_stream.(also "the_stream")
Any idea ?

[wysota]

Show us the actual code. If this is (almost) your real code then the behaviour is correct -- you are overwriting your own stack. If you write enough bytes, you'll crash your app

[stampede]

If this is how the constructor really looks like, then "Mybuffer is private to W_stream."" is not true. You are creating new variable mybuff, which is different from this->mybuff. This new variable is destroyed when constructor exits, so the_stream keeps invalid buffer pointer. Remove the "char mybuff[]" declaration from constructor.
Another thing:

the_stream->rdbuf()->pubsetbuf(mybuffer,265536);

the_stream->rdbuf()->pubsetbuf(mybuffer,265536);

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use sizeof() instead of hard-coded numbers:

the_stream->rdbuf()->pubsetbuf(mybuffer,sizeof(mybuff)/sizeof(char));

the_stream->rdbuf()->pubsetbuf(mybuffer,sizeof(mybuff)/sizeof(char));

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Its easier to correct the number in one place.