Clarify autom4te debugging tips.

* doc/autoconf.texi (Debugging via autom4te): Fix example from
previous commit, and add clarification.

Signed-off-by: Eric Blake <ebb9@byu.net>

diff --git a/ChangeLog b/ChangeLog
index 4ed5149ccea8bb4b6ec0fdf4668850763c8b50a4..4ecd0d822ce6132c5531483f3f8a51529a4ee785 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2009-07-25  Bruno Haible  <bruno@clisp.org>
+
+       Clarify autom4te debugging tips.
+       * doc/autoconf.texi (Debugging via autom4te): Fix example from
+       previous commit, and add clarification.
+
 2009-07-25  Eric Blake  <ebb9@byu.net>
 
        Document some autom4te debugging tips.

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 0b61e35d0d004abb49325eaf737b9bd617517d90..39286fd4997672d5504bd768926ec3aecd5b59bf 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -12454,39 +12454,25 @@ $ @kbd{autoconf --trace='AC_INIT:version is $2'}
 version is 2.63b.95-3963
 @end example
 
-Another trick is using @code{m4_errprintn} to output debugging messages
-to standard error with no further m4 expansion, and without interfering
-with the post-processing done to standard output.  For example, contrast
-these two attempts to learn how @code{m4_dquote} is implemented:
+Another trick is to print out the expansion of various m4 expressions to
+standard error or to an independent file, with no further m4 expansion,
+and without interfering with diversion changes or the post-processing
+done to standard output.  @code{m4_errprintn} shows a given expression
+on standard error.  For example, if you want to see the expansion of an
+autoconf primitive or of one of your autoconf macros, you can do it like
+this:
 
-@smallexample
-$ @kbd{cat <<\EOF > foo.m4}
-m4_init
-try one: [m4_dquote is ]m4_defn([m4_dquote])
-m4_divert([0])dnl
-try two: [m4_dquote is ]m4_defn([m4_dquote])
-m4_dquote([hi])
-EOF
-$ @kbd{autom4te --language=m4sugar -o foo foo.m4}
-foo.m4:2: error: possibly undefined macro: m4_dquote
-      If this token and others are legitimate, please use m4_pattern_allow.
-      See the Autoconf documentation.
-$ @kbd{cat foo}
-try two: m4_dquote is [$@@]
-[hi]
-$ @kbd{cat <<\EOF > foo.m4}
-m4_init
-m4_errprintn([try one: m4_dquote is ]m4_defn([m4_dquote]))
-m4_divert([0])dnl
-m4_errprintn([try two: m4_dquote is ]m4_defn([m4_dquote]))dnl
-m4_dquote([hi])
+@example
+$ @kbd{cat <<\EOF > configure.ac}
+AC_INIT
+m4_errprintn([The definition of AC_DEFINE_UNQUOTED:])
+m4_errprintn(m4_defn([AC_DEFINE_UNQUOTED]))
+AC_OUTPUT
 EOF
-$ @kbd{autom4te --language=m4sugar foo.m4}
-try one: m4_dquote is [$@@]
-try two: m4_dquote is [$@@]
-$ @kbd{cat foo}
-[hi]
-@end smallexample
+$ @kbd{autoconf}
+@error{}The definition of AC_DEFINE_UNQUOTED:
+@error{}_AC_DEFINE_Q([], $@@)
+@end example
 
 @node Programming in M4sh
 @chapter Programming in M4sh