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Re: Bug in #include guards

From: Alexander Belopolsky
Subject: Re: Bug in #include guards
Date: Tue, 2 Oct 2001 12:28:58 -0400 (EDT)

Akim Demaille writes:
 > >>>>> "marc-alexandre" == marc-alexandre autret <address@hidden> writes:
 > Don't go into the hexa stuff please, `_' is fine for non
 > alphanumeriscoral characters.

I disagree.  The whole point of include guards is that they are unique
and no two files can ever have the same guards.  If you replace
non-alphanumeric characters with _ it is possible to have include
files with different names but the same include guard.  At least three
non-alphanumeric characters from the basic character set: '/', '.' and
'-' are very commonly used in include file names.  Three more ':', ','
and '+' are less common, but not unheard of.  If you fold them all
(and '_' itself) into '_' there is high risk of collision.

However I am not particularly keen on 'hexa stuff', if you suggest any
other scheme that produces unique guards from path names I can recode
my patch.

Alexander Belopolsky | Renaissance Technologies Corp.
600 Route 25A | East Setauket | NY 11733-1249
PH: 631-444-7125 | FAX: 631-444-7009

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