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Re: m4_chomp


From: Eric Blake
Subject: Re: m4_chomp
Date: Fri, 14 Nov 2008 10:05:04 -0700
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According to Eric Blake on 11/14/2008 8:06 AM:
> Stripping one newline just did the wrong thing.  As long as we are at risk
> of doing it wrong by stripping one, it is just as easy to strip them all.
>  And in the case of m4_esyscmd_s, you actually want to strip all newlines,
> to match `` behavior.  But yes, limiting to one newline is as easy as
> changing the regexp in m4_chomp from /*$ to /?$.

For that matter, chomping only one newline makes it possible to avoid a
regex, for faster m4_chomp performance.  Thanks for the idea:

m4_define([m4_chomp],
[m4_format([[%.*s]], _m4_index(m4_translit([$1],[
]]m4_dquote(_m4_defn([m4_cr_all]))[,
  [/]]m4_format([%255s],)[)-, [/-]),[$1])])

I guess I'll rework my series, and see what sort of performance hit (if
any) we get by rewriting m4_expand to always add a newline then chomp it.
 It certainly makes m4_expand more robust, at the expense of a corner case
for expansions that end in dnl without newline (fortunately such
expansions are rare).

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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