Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!njin!princeton!phoenix!mbkennel
From: mbkennel@phoenix.Princeton.EDU (Matthew B. Kennel)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Question about Bison
Message-ID: <3889@phoenix.Princeton.EDU>
Date: 8 Oct 88 21:28:03 GMT
References: <8246@cit-vax.Caltech.Edu>
Reply-To: mbkennel@phoenix.Princeton.EDU (Matthew B. Kennel)
Organization: Princeton University, NJ
Lines: 41

In article <8246@cit-vax.Caltech.Edu> janin@tybalt.caltech.edu (Adam L. Janin) writes:
>I just installed Bison on a Mac II and I'm having a problem when linking.
>Using bison.simple, I get a link error (missing functions alloca and bcopy).
>When I use bison.hairy (using the %semantic_parser command), I get other link
>errors (several missing functions).  I assume I should simply replace 
>alloca with NewPtr and bcopy with MemCopy.  Is this correct?
>	Thanks,
>		Adam Janin
>		janin@tybalt.caltech.edu  or  janin@csvax.caltech.edu

Oh, no, it's the "alloca" argument all over again.  I believe that alloca
is a function to allocate local storage.  The difference between it and
malloc is that all storage allocated by alloca will get disposed
_automatically_ whenever the function that called alloca returns.

The problem comes in on the "automatically" part.  I believe that in general
implementing "alloca" can be quite difficult on some architectures, and often
needs some pretty close consideration on the part of the compiler.  Some
people have argued that just having the ability to do an "alloca" implemented
can seriously slow down function calls, especially on some RISC machines.

Thus, some people have argued that "alloca" should be abolished from use,
replaced, by explicit allocate/free calls.  Unfortunately, Richard Stallman
is pretty dogmatically in favor of the other side, and so it looks like
"alloca" will continue to be used in many FSF programs (of which Bison and
Emacs are examples).

The bottom line for your specific problem is:

You might either have to write "alloca" (Which might be quite difficult).

Or, you have to modify Bison to use malloc and the appropriate free call
explicitly.  In this respect, the UNIX call "malloc" is analogous to the
MacOS call "NewPtr."  If you replace all calls to "alloca" to "malloc" or
"NewPtr", it will still work, but you will get serious memory fragmentation
over time.

I think that "bcopy" does just about the same thing as "BlockMove".

Matt Kennel
mbkennel@phoenix.princeton.edu