Path: utzoo!attcan!uunet!husc6!mailrus!ames!amdahl!apple!dan
From: dan@Apple.COM (Dan Allen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Flex fast lexical analyzer for MPW announcement.
Keywords: %Globaldata Sucks Wind.
Message-ID: <10896@apple.Apple.Com>
Date: 23 May 88 05:15:27 GMT
References: <8534@dartvax.Dartmouth.EDU>
Reply-To: dan@apple.UUCP (Dan Allen)
Organization: Apple Computer Inc, Cupertino, CA
Lines: 39

I agree that a 32K global data limit is stupid.  But the workaround in
most cases is so trivial (especially in C) that why waste time worrying
about it?  USE THE HEAP!  If a program needs big buffers or big arrays,
then use New in Pascal, malloc in C, or NewPtr in general for the Mac.
And with MultiFinder around, if a large buffer is only temporary, you
can request the space from MultiFinder's heap and have your application
look like a hero by running in a much smaller MultiFinder partition!
(This last suggestion may not work real well with MPW tools, but works
fine in apps.)

It is very rare for an application to REALLY NEED more than 32K of
global data.  I submit that if an app is using more than 32K, then it is
written wrong, that is, the allocation of the space should be at a more
local scope or whatever.

I have done a fair amount of work with several NON-TRIVIAL applications
for the Mac.  You may have even heard of them.

HyperCard 1.2	312732 bytes of code,  25872 bytes of global data = 8%
MPW Shell 2.0+  179874 bytes of code,  20674 bytes of global data = 11%

The percentages are simply global data divided by size of code (not
including resources-just real live CODE).  The MPW percentage is
actually a bit high because it is written in C which does a lot of
global data initialization which is included in the code size, whereas
HyperCard is written in MPW Pascal and the initialization code is not
automatic, although HyperCard does initialize portions of its global
data.

So anyway, I do not think that global data should be as big a deal.  If
you have a specific problem, I would be interested in hearing about it
to see if my conjecture (that no well written app NEEDS more than 32K of
global data) is actually true or not.

Use the heap, and then if you still need more memory, buy more SIMMs.

Dan Allen
Software Explorer
Apple Computer