[SCM] GNU Autoconf source repository branch, master, updated. v2.63b-96-gde8a83c

[Eric Blake]

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- Log -----------------------------------------------------------------
commit de8a83c3e977937782ef3ce686909d7fa7538e81
Author: Eric Blake <address@hidden>
Date:   Sat Jul 25 06:51:59 2009 -0600

    Document some autom4te debugging tips.
    
    * doc/autoconf.texi (Debugging via autom4te): New node.
    Suggested by Bruno Haible.
    
    Signed-off-by: Eric Blake <address@hidden>

commit 3963d3ad3ef46190650474d56a9e750648a23036
Author: Eric Blake <address@hidden>
Date:   Sat Jul 25 06:24:49 2009 -0600

    Fix font-lock.
    
    * configure.ac (ac_cv_unsupported_fs_chars): Make editing easier.
    
    Signed-off-by: Eric Blake <address@hidden>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog         |    7 ++++++
 configure.ac      |    4 +-
 doc/autoconf.texi |   62 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 5daef4d..4ed5149 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2009-07-25  Eric Blake  <address@hidden>
 
+       Document some autom4te debugging tips.
+       * doc/autoconf.texi (Debugging via autom4te): New node.
+       Suggested by Bruno Haible.
+
+       Fix font-lock.
+       * configure.ac (ac_cv_unsupported_fs_chars): Make editing easier.
+
        Let autoheader see through m4 macros in AC_DEFINE.
        * lib/autoconf/general.m4 (AC_DEFINE_TRACE): Expand macro before
        tracing its name.
diff --git a/configure.ac b/configure.ac
index 0f2aec1..0d579f8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -69,9 +69,9 @@ fi
 AC_SUBST([ac_cv_sh_n_works])
 
 AC_MSG_CHECKING([for characters that cannot appear in file names])
-AC_CACHE_VAL( [ac_cv_unsupported_fs_chars],
+AC_CACHE_VAL([ac_cv_unsupported_fs_chars],
 [ac_cv_unsupported_fs_chars=
-for c in '\\' '"' '<' '>' '*' '?' '|'
+for c in '\\' \" '<' '>' '*' '?' '|'
 do
   touch "conftest.t${c}t" 2>/dev/null
   test -f "conftest.t${c}t" && rm -f "conftest.t${c}t" && continue
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 34df30b..0b61e35 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -430,6 +430,7 @@ Programming in M4
 * M4 Quotation::                Protecting macros from unwanted expansion
 * Using autom4te::              The Autoconf executables backbone
 * Programming in M4sugar::      Convenient pure M4 macros
+* Debugging via autom4te::      Figuring out what M4 was doing
 
 Programming in M4sh
 
@@ -9414,6 +9415,7 @@ matter of fact, @emph{anything that is not documented 
must not be used}.
 * M4 Quotation::                Protecting macros from unwanted expansion
 * Using autom4te::              The Autoconf executables backbone
 * Programming in M4sugar::      Convenient pure M4 macros
+* Debugging via autom4te::      Figuring out what M4 was doing
 @end menu
 
 @node M4 Quotation
@@ -12426,6 +12428,66 @@ Any token matching @var{pattern} is allowed, including 
if it matches an
 @code{m4_pattern_forbid} pattern.
 @end defmac
 
address@hidden Debugging via autom4te
address@hidden Debugging via autom4te
address@hidden debugging tips
address@hidden autom4te debugging tips
address@hidden m4sugar debugging tips
+At times, it is desirable to see what was happening inside m4, to see
+why output was not matching expectations.  However, post-processing done
+by @command{autom4te} means that directly using the m4 builtin
address@hidden is likely to interfere with operation.  Also, frequent
+diversion changes and the concept of forbidden tokens make it difficult
+to use @code{m4_defn} to generate inline comments in the final output.
+
+There are a couple of tools to help with this.  One is the use of the
address@hidden option provided by @command{autom4te} (as well as each
+of the programs that wrap @command{autom4te}, such as
address@hidden), in order to inspect when a macro is called and with
+which arguments.  For example, when this paragraph was written, the
+autoconf version could be found by:
+
address@hidden
+$ @kbd{autoconf --trace=AC_INIT}
+configure.ac:23:AC_INIT:GNU Autoconf:2.63b.95-3963:bug-autoconf@@gnu.org
+$ @kbd{autoconf --trace='AC_INIT:version is $2'}
+version is 2.63b.95-3963
address@hidden example
+
+Another trick is using @code{m4_errprintn} to output debugging messages
+to standard error with no further m4 expansion, and without interfering
+with the post-processing done to standard output.  For example, contrast
+these two attempts to learn how @code{m4_dquote} is implemented:
+
address@hidden
+$ @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])
+EOF
+$ @kbd{autom4te --language=m4sugar foo.m4}
+try one: m4_dquote is [$@@]
+try two: m4_dquote is [$@@]
+$ @kbd{cat foo}
+[hi]
address@hidden smallexample
+
 @node Programming in M4sh
 @chapter Programming in M4sh
 


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