Amiga Computing - Commodore Is Awesome

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A ILOCATION AND I
DEALLOCATION
From time to time in my assembler
columns etc_ I've talked about
my stack-based schemes used to
handle allocation and deallocation
operations. Now you are going to
get the chance to see how I do it
from C when several different
code modules are in use. Stacks,
of course, store things on a last in
First out basis and what my
scheme does is ensure that ANY
routine which successfully allocates
or opens some returnable or
closeable system resource pushes
the address of a corresponding
closedown routine onto a stack.
To allow for allocation failures
as the program runs, I adopt the
convention of having all allocation
routines return error numbers that
indicate whether they've succeeded
or not Providing these conventions
are followed, a program
is able to perform its closedown
operations by using a loop to pull
those deallocation routine pointers
from the stack and executing
the corresponding routines. The
beauty of this approach is that the
stack automatically deallocates
things in the reverse order to
the original allocations - things
which are allocated last get deallocated
first (a good, safe, general
method to adopt with all Amiga
programs).
How do I set up the allocation/de-allocation
code and get
the right pieces of code executed
at the appropriate times? The best
idea is to look at some example
fragments. Listing 1 shows two
routines which open and close the
Intuition library. Notice that the
UWE AllocateResourtelLIEWE tount,WITE f*listC3)Evoid))
UWE i, error_ntiober;
for (i:0;1