On Sun, 7 Mar 2010, John Calcote wrote:
The idea here of course is that the unwanted situation whereby the same
config.h file is inadvertently included in the same translation unit twice
could be avoided.
As an aside: It's interesting to note that gcc's preprocessor has built-in
functionality to automatically guard against this situation.
It is also interesting to note that it is usually ok for the content
of the header file to be parsed any number of times. The only
exception might be with some weird macro expansion (but that would be
a bug).
The conditional inclusion of content is only an optimization. The
content of the typical config.h is quite easy to parse. Opening the
file to inspect it is surely much more overhead than whatever parsing
overhead is saved by the extra conditional. This becomes more and
more true as time goes by. In the early '90s the benefit was
tangible, but probably not at all any more.
A cost/benefit analysis should show that this effort is not worth
doing.
Bob
--
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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