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From: brian@babbage.csus.edu (Brian Witt)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: REVIEW:  Comeau C++ compiler
Summary: objC translation
Keywords: programming, language, C++, compiler, objective-C
Message-ID: <1991Apr23.163448.26011@csusac.csus.edu>
Date: 23 Apr 91 16:34:48 GMT
References: <36963@ditka.Chicago.COM> <1991Apr17.174759.16250@jato.jpl.nasa.gov> <20862@cbmvax.commodore.com>
Sender: usenet@csusac.csus.edu (News account (alt))
Organization: California State University, Sacramento
Lines: 52

In article <20862@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>In article <1991Apr17.174759.16250@jato.jpl.nasa.gov> jdickson@jato.Jpl.Nasa.Gov (Jeff Dickson) writes:
>
>>	Since this C++ compiler rewrites your C++ into plain'ol C, does it
>>do a good job? Say compared to if a human performed the translation manually.
>
>When a C++ compiler translates C++ code into C, it is doing much the same thing
>that a C compiler does when it translates C into object code.

There are a few oddities of coercien that go on, behind the scenes.
For the objective-C (TM) like translator I built, for each message
invokation, the "outter most" addition the translator does it put
a typecast on the function call.  Using a lead in Dr. Cox's book,
I typecast the function _msg() to a function that returns the
required type.  This is NOT typecasting the return value (which can
cause a conversion to take place, ie int --> float).  Function _msg()
by default returns a pointer type.

with this define:          extern void    *_msg( void *, SEL, ... );
For instance, the line:    char  *name = [bytestring name];
turns into:

char  *name = (*((char * (*)()) _msg))( bytestring ,(/* name */_ocSAnoname[9])) ) );

(_ocSAnoname[] holds method selectors. it's long, but it works! )

>  Given the extra complexities of
>the C++ language, even if you wanted to do a hand translation, and felt you 
>could do better, it would take forever, and your head would eventually explode.

In my OCT system, I've found that a line length doubles when converted
from objective-C (TM) into plain old "C".  Since OCT using dynamic binding
throughout, you have to jump to a helper function.  With static binding
(like that in C++), your milage may vary...

>-- 
>Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
>   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy

objective-C is a trademark of Stepstone, Inc.

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         brian witt         |   brian@babbage.ecs.csus.edu
    You are what you click  |  (and if you click it twice...)
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         brian witt         |   brian@babbage.ecs.csus.edu
    You are what you click  |  (and if you click it twice...)
  Not representing Cal State Sacramento, the ECS dept, or Iraq