🚀 go-pugleaf

In article <41si6s$4qs@lyra.csx.cam.ac.uk>, nmm1@cus.cam.ac.uk (Nick
Maclaren) writes: 
<snip>
|> This is the usual reason, but be warned that SOME compilers will parse

The SOME above refers to every ANSI compliant compiler. The preprocessor
works after the text has been `tokenized' (Actually, pp-token-ized), and
hence invalid tokenization (incomplete character or string constants or
incomplete comments) can lead to problems. In addition, the skipping is not
`total': preprocessing directive _names_ are processed (though not the rest
of them: except that they are pp-tokenized of course), and so invalidly names
preproprecessing directives can cause problems.

|> (or partially parse) some of the excluded text.  You should therefore
|> not use this trick to exclude syntactically invalid C.  The reason for

It can be syntactically invalid C: it must not be _lexically_ invalid C.
Thus, you can skip over `The quick brown fox.' even if you have defined no
macros (and then it is clear that it cannot be `syntactically' valid C code),
and yet you cannot skip over `My father's house' because the unmatched single
quote leads to problems with parsing the text lexically.

|> this problem is that the standard is unclear in this area.

Why do you claim the _standard_ is unclear in this area? Which standard are
you talking about? There does not seem to be any hint of lack of clarity in
the ANSI standard!

|> 
|> >By the way, these constructs should normally not appear in finished code.
|> >I use them (I hope) exclusively in code that I'm currently writing or
|> >changing. I take them out when I'm done.
|> 
|> There is one case where they SHOULD appear in finished code:  that is
|> where the code is left as an example, and cannot be used without further
|> editing.  I use '#if 0 == 1' AND comment the code in such cases.

To each his own. I prefer `#if 0' over `#if 0 == 1'. But if someone wanted to
write `#if (0 == 1) != (0 == 1)', or followed some other `higher principle'
by needless obfuscation and/or verbosity, I wouldn't complain either.

Cheers
Tanmoy
-- 
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