Re: 2.62 AT_SETUP limitations

[Eric Blake]

Eric Blake <ebb9 <at> byu.net> writes:

> > I find it rarely pays to play the guessing game of "surely the user will 
> > never do *this*".  Moreover, I'm betting that the user will never guess 
> > that this bizarre string is actually special to autotest.
> 
> Magic line-noise strings don't just affect autotest, but all m4sugar-based 
> languages, including autoconf itself.
> 
> >  At the very 
> > least, can this new limitation be mentioned in the manual?  Or did I miss 
> > it?
> 
> So yes, it would probably be worth adding a blurb in the m4sugar 
documentation 

Like so:

>From c11e71ae5663c64cac637031563d4b4de1cc3390 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Thu, 24 Apr 2008 09:31:16 -0600
Subject: [PATCH] Mention m4sugar's internal quote strings.

* doc/autoconf.texi (Quadrigraphs): Mention alternate quote used
in m4sugar, and how to still output it literally.
* tests/m4sugar.at (m4@&address@hidden): And test it.
Reported by Joel E. Denny.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog         |    8 ++++++++
 doc/autoconf.texi |   21 ++++++++++++++++++---
 tests/m4sugar.at  |    7 +++++++
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 5bb1e97..fad30e7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2008-04-24  Eric Blake  <address@hidden>
+
+       Mention m4sugar's internal quote strings.
+       * doc/autoconf.texi (Quadrigraphs): Mention alternate quote used
+       in m4sugar, and how to still output it literally.
+       * tests/m4sugar.at (m4@&address@hidden): And test it.
+       Reported by Joel E. Denny.
+
 2008-04-23  Eric Blake  <address@hidden>
 
        Allow unbalanced () in m4_expand.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index b6ae602..ff7ffc7 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -9629,7 +9629,13 @@ expression @samp{[^[]}, which matches any character 
other than @samp{[}.
 This expression contains unbalanced brackets so it cannot be put easily
 into an M4 macro.
 
-You can work around this problem by using one of the following
+Additionally, there are a few m4sugar macros (such as @code{m4_split}
+and @code{m4_expand}) which internally use special markers in addition
+to the regular quoting characters.  If the arguments to these macros
+contain the literal strings @samp{-=<@{(} or @samp{)@}>=-}, the macros
+might behave incorrectly.
+
+You can work around these problems by using one of the following
 @dfn{quadrigraphs}:
 
 @table @samp
@@ -9661,9 +9667,18 @@ The empty quadrigraph can be used:
 
 Trailing spaces are smashed by @command{autom4te}.  This is a feature.
 
address@hidden to produce other quadrigraphs
address@hidden to produce quadrigraphs and other strings reserved by m4sugar
+
+For instance @samp{@@<@@&t@@:@@} produces @samp{@@<:@@}.  For a more
+contrived example:
 
-For instance @samp{@@<@@&t@@:@@} produces @samp{@@<:@@}.
address@hidden
+m4_define([a], [A])m4_define([b], [B])m4_define([c], [C])dnl
+m4_split([a )@}>=- b -=<@{( c])
address@hidden, [], [B], [], [c]
+m4_split([a )@}@@&t@@>=- b -=<@@&t@@@{( c])
address@hidden, [)@}>=-], [b], [-=<@{(], [c]
address@hidden example
 
 @item to escape @emph{occurrences} of forbidden patterns
 
diff --git a/tests/m4sugar.at b/tests/m4sugar.at
index 8dc1279..69cb74b 100644
--- a/tests/m4sugar.at
+++ b/tests/m4sugar.at
@@ -170,6 +170,11 @@ m4_split([abcde], [bd])
 m4_split([abcde], [[bd]])
 m4_split([foo=`` bar=''])
 m4_split([foo='' bar=``])
+dnl these next two are from the manual; keep this in sync if the internal
+dnl quoting strings in m4_split are changed
+m4_define([a], [A])m4_define([b], [B])m4_define([c], [C])dnl
+m4_split([a )}>=- b -=<{( c])
+m4_split([a )}@&t@>=- b -=<@&address@hidden( c])
 ]],
 [[
 
@@ -184,6 +189,8 @@ m4_split([foo='' bar=``])
 [a], [c], [e]
 [foo=``], [bar='']
 [foo=''], [bar=``]
+[a], [], [B], [], [c]
+[a], [)}>=-], [b], [-=<{(], [c]
 ]])
 
 AT_CLEANUP
-- 
1.5.5.1