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pointers--avoiding a memory leak [message #39425]

Wed, 19 May 2004 12:20

MKatz843
Messages: 98
Registered: March 2002

Member

Here's a simple Pointers 101 question for the pointer gurus.

Suppose you have a structure with a pointer field
s = {a:10, b:ptr_new(10)}

Somewhere down the line you want to update the value of *s.b making it
equal to the value contained in a another pointer, say *q = 20. After
the assignment, you'll no longer need the q pointer.

So which is a better strategy?

#1)
ptr_free, s.b
s.b = q

#2)
*s.b = *q
ptr_free, q

#3)
s.b = q ;--- what becomes of the old s.b in this case?

I can see how #1 is memory-efficient because only the pointer is
passed. I can see that #2 is memory inefficient because the values are
swapped. This could be slower if the value is a large array. I can see
how #3 might result in a memory leak, since the old s.b value could be
stranded in memory with no pointer pointing to it. Am I right about
these? What else should I be thinking about in the above situation?

Thanks,
M. Katz

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By: MKatz843 on Wed, 19 May 2004 12:20

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