Subject: [PATCH] Swallow m4traces that have no file/line number

From: Christophe de Dinechin <[email-masked]>
Date: Tue, 7 Mar 2017 23:00:46 +0100

The symptoms are something like:

  Use of uninitialized value $msg in concatenation (.) or string at /usr/local/Cellar/autoconf/2.69/bin/autom4te line 1032.
  Use of uninitialized value $stacktrace in pattern match (m//) at /usr/local/Cellar/autoconf/2.69/bin/autom4te line 1032.
  unknown channel m4trace: -1- AS_VAR_APPEND(ac_configure_args, " '$ac_arg'")
   at /usr/local/Cellar/autoconf/2.69/share/autoconf/Autom4te/Channels.pm line 638.
      Autom4te::Channels::msg('m4trace: -1- AS_VAR_APPEND(ac_configure_args, " \'$ac_arg\'")\x{a}', undef, 'warning: ', 'partial', 0) called at /usr/local/Cellar/autoconf/2.69/bin/autom4te line 1032

The root cause is m4 traces without a file/line number shown.

So instead of something like:

   m4trace:configure.ac:48: -1- ...

you have something like:

  m4trace: -1- ...

In the scenarios I ran into, this is due to some error that throws m4 out.
Eliminating these messages from the temporary m4 file being generated
(which will not complete anyway) is sufficient for the rest of autoconf
to complete, until it prints errors.

In my case, the final error looks like:

  common/Makefile.am:20: error: Libtool library used but 'LIBTOOL' is undefined
  common/Makefile.am:20:   The usual way to define 'LIBTOOL' is to add 'LT_INIT'
  common/Makefile.am:20:   to 'configure.ac' and run 'aclocal' and 'autoconf' again.
  common/Makefile.am:20:   If 'LT_INIT' is in 'configure.ac', make sure
  common/Makefile.am:20:   its definition is in aclocal's search path.
  autoreconf: automake failed with exit status: 1

But I've seen various reports for other root causes that ran into the same
problem (see bug report)

Signed-off-by: Christophe de Dinechin <[email-masked]>
---
 bin/autom4te.in | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/bin/autom4te.in b/bin/autom4te.in
index 964ac1a..b3f3831 100644
--- a/bin/autom4te.in
+++ b/bin/autom4te.in
@@ -821,6 +821,8 @@ EOF
   my $traces = new Autom4te::XFile ($tcache . $req->id, "<");
   while ($_ = $traces->getline)
     {
+      # Traces without file/line
+      next if (m{^m4trace: -(\d+)- ([^(]+)\((.*)$});
       # Trace with arguments, as the example above.  We don't try
       # to match the trailing parenthesis as it might be on a
       # separate line.
-- 
2.10.1 (Apple Git-78)