[2914] in java-interest
Re: Preprocessor features
daemon@ATHENA.MIT.EDU (patl@asimov.volant.org)
Fri Oct 20 13:53:58 1995
From: patl@asimov.volant.org
Date: Fri, 20 Oct 1995 08:40:19 -0700
To: java-interest@java.sun.com, mtravis@ncsa.uiuc.edu
|> In actuality, you can use the C/C++ preprocessor to process *any* source
|> file before compilation, even Java source. The problem with this is that
|> you lose all pretty formatting and comments as part of the preprocessing.
|> If you preprocess as part of the compilation process, as is done in C and
|> C++, then this may not be a significant issue. I was porting some C code
|> that was so heavily-dependent on the preprocessor, that to remove the
|> #define's and such would have required basically a rewrite from scratch.
|> By maintaining the use of the preprocessor, I saved weeks of time. I was
|> using Borland's stand-alone preprocessor which comes with Borland C++.
There are a couple of other problems with using the C/C++ preprocessor
as a general-purpose macro processor:
1. It has certain C/C++ semantics built in, with no way to turn them off.
For example, if your text happens to contain '/*', the preprocessor
starts eating text and looking for a '*/'. Which is ok if your source
happens to be sufficiently c-like to use that as comment notation...
ANSI string concatenation, and ## processing can also cause problems.
2. The built-in pre-defined macros can cause unexpected substitutions,
and the specific words that cause problems will vary from system to
system. Of course, this can also be a problem in C/C++ programs
themselves. A few years ago a co-worker was having a hell of a time
trying to figure out why he was getting a syntax error on a declaration.
I had to point out that the preprocessor was replacing his variable name
(unix) with a 1 because it happened to match one of the predefined macros
for that system.
-Pat
My opinions are my own. For a small royalty, they can be yours as well...
Pat Lashley, Senior Software Engineer, Henry Davis Consulting
patl@Phoenix.Volant.ORG || http://Phoenix.Volant.ORG/ || lashley@netcom.com
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