Re: A comment-finding hack for hppa I found useful

[Michael Meissner <meissner at cygnus dot com>]

On Tue, Jul 11, 2000 at 12:10:52PM -0700, Nick Clifton wrote:
> Hi Alan,
> 
> :    I found the following hack useful when debugging glibc sources
> : for hppa.  The comment in the first hunk below indicates why it's
> : useful, but I'm ambivalent as to whether this belongs in the
> : official sources.
> 
> So basically the problem is that (for the hppa) the comment chracater,
> (';') is the same as the line seperator character for lots of other
> assemblers, and that tihs leads to confusion, especially when writing
> C asm statements ?
> 
> I guess I have no objections to adding the feature, although I think
> that it will only very occaisionally be useful.  perhaps it could be
> part of the output with the -D switch ?
> 
> : PS. Question for the language experts.  "#if MACRO" or "#ifdef MACRO",
> : which is preferred?  Given MACRO is either undefined or evaluates to 1,
> : there is no difference really (except I believe some really old compilers
> : don't even supprt #ifdef)

At the time of the original C standard was being produced (1984 or 1985 being
the first meeting), there were no known compilers still in use that did not
support #ifdef (K&R-1 mentions both #ifdef and #if).  I do recall having
#ifdef's and a preprocessor when I was working on a UNIX V6 system in 1979
(though you had to make sure the first byte of the file was '#' or else the
preprocessor was not run, and it had the original wacky structure rules).  The
default compiler on SunOS does support #if name and #if defined(name).

> I had not heard about old compilers not supporting #ifdef, but I think
> from a very strict point of view, I would prefer '#ifdef MACRO" over
> "#if MACRO" since this makes clear that all that is being tested is
> the fact that MACRO is defined, not what value it might happen to
> have.

I agree with Nick.

-- 
Michael Meissner, Red Hat, Inc.
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