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From: leech@tlab1.cs.unc.edu (Jonathan Leech)
Newsgroups: comp.lang.c++
Subject: Re: Objective-C vs C++
Message-ID: <4988@thorin.cs.unc.edu>
Date: 1 Nov 88 17:46:31 GMT
References: <8335@nlm-mcs.arpa> <3438@jpl-devvax.JPL.NASA.GOV> <8375@alice.UUCP> <913@taux01.UUCP>
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Reply-To: leech@tlab1.UUCP (Jonathan Leech)
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In article <913@taux01.UUCP> cjosta@taux01.UUCP (Jonathan Sweedler) writes:
>In article <8375@alice.UUCP> ark@alice.UUCP (Andrew Koenig) writes:
>>	A good C++ programmer can convert about 1,000 lines of
>>	old C an hour to C++.  Converting ANSI C should be faster.
>Yeah, right.  An then how about debugging?  The whole point about
>*compatability* is that you don't have to do this conversion that
>is NEVER as easy as it seems.	And what do you mean by "good" C++
>programmer?  Certainly not the same programmer that learned C++
>"in a day or less."  Everything looks good in the best-case light.
>I don't think things are as easy in real life.

    Just as a point of reference: I recently converted a screen editor
which I maintain to be compilable under both C++ and C. It was ~25000
lines of C code, not very well designed, but highly portable. It took
about 2 days.  The major problems I encountered were:

    - lack of function prototypes. I modified lint to generate
	prototypes (these modifications should be on comp.sources.unix
	soon).

    - Old-C style declarations of formal arguments which cfront
	handled incorrectly. There were a few dozen of these and they
	were annoying to fix, but it is a cfront problem, not C++.

    - Functions that use unportable argument-passing conventions
	e.g. the old classic (written before varargs existed):
	    int error(str, a1, a2, a3, a4, a5) char *str; {
		fprintf(stderr, str, a1, a2, a3, a4, a5);
	    }
	the problem here was a clash between the C++ prototype
	required for such functions to be used as desired:
	    extern int error(char * ...)
	and the actual declaration.

    Debugging time for the C++ version (after making it compile) was
0. It worked right off the bat. C++ uncovered some potential
portability problems I had not seen with lint. True, I'd never
encountered these problems on machines ranging from PCs to DG Eclipse
to VAX/VMS etc... but I appreciated finding them anyway.

    I would be happier if AT&T fixed the annoying little cfront bugs
and provided some way to not need prototypes so large, complex C
programs could be more easily converted, but the amount of effort
involved in this conversion was not unreasonable.

--
    Jon Leech (leech@cs.unc.edu)    __@/
    ``The law of gravitation is different from many of the others...
      there are many places where gravity has its practical
      applications as far as the Universe is concerned.''
	- R. P. Feynman, _The Character of Physical Law_