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From: earleh@eleazar.dartmouth.edu (Earle R. Horton)
Newsgroups: comp.sys.mac.programmer
Subject: Re: using Bison and Flex with LSC
Keywords: yacc and lex on the mac
Message-ID: <13619@dartvax.Dartmouth.EDU>
Date: 24 May 89 16:33:32 GMT
References: <1133@munmurra.mu.oz>
Sender: news@dartvax.Dartmouth.EDU
Reply-To: earleh@eleazar.dartmouth.edu (Earle R. Horton)
Organization: Thayer School of Engineering
Lines: 65

In article <1133@munmurra.mu.oz> jkjl@munmurra.mu.oz (John Lim) writes:
>I'm been busy porting the some GNU C code to the mac. Here's a little
>hint if you use Bison and Flex with LSC like i do. Bison and Flex were
>compiled using MPW C which maps '\n' to carraige return, not linefeed.
>
>LSC maps '\n' to linefeed as in UNIX. But the symbol tables in both
>Bison and Flex expect '\n' defined in your .y and .l files to be
>carraige returns. It took me 4 stupid hours of debugging to realize this
>( I dont own MPW C, just TML Pascal //). 
>

     The latest edit of flex writes out two character tables: one for
('\n' == 10) and another for ('\n' == 13).  A preprocessor macro is
used to decide, at the time of compilation of the flex-produced
C-code, what the end-of-line character will be.  This means that the
output C-code can be used directly with LSC, MPW C, or with your
favorite MSDOS C compiler.  The program is on sumex.  If you don't
have internet ftp, you can get it from me by sending a pre-formatted
800k disk, mailer, and return postage to the address at the end of
this article.  Other goodies will be included, up to disk capacity.
If you're porting GNU or another PD code to the Mac, by all means
include some on the disk!

>What this means when porting such code to LSC, use
>
>1. The "b" flag for reading files (binary mode).
>
>2. Change all instances of '\n' in the .c generated files to '\r'
>  (and the .h files too !).
>
     No longer necessary if you get the new edit of flex.  All
instances of '\n' have been replaced with EOLCHAR, and you control
what this means.  Make sure that your choice of EOLCHAR agrees with
your choice whether or not to use binary mode, however!

>3. insert the line in the *.tab.c files:
>	#define bcopy(x,y,z) BlockMove(x,y,z)
>
     If you put this in your "bison.simple" file, then you only have
to do it once.
     
>4. Rewrite alloca() or if you have lots of memory ...
>	#define alloca(x)	mlalloc((long) (x)) /* mem not freed */

     A better solution is to write your own "yyoverflow()" routine.
Look at the "bison.simple" file to see how this might be done.  

     A problem exists with assembler versions of alloca() that make
space on the stack frame of the caller.  Sometimes these are
incompatible with the C compiler's handling of the stack.  You have to
look at the assembler- (or disassembled machine-) code produced by the
function which calls alloca() for potential problems.  If you are not
reasonably proficient in assembler, you might not be able to figure
out whether you have the proper alloca() for use with your compiler.

     I did the flex port to the Mac.  I supplied the alloca() that
comes with it.  I don't have any idea whether a direct translation of
this routine to LSC will be safe to use.

Earle R. Horton
23 Fletcher Circle	# No stamps -> You don't get your disk back.
Hanover, NH 03755

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