Subject: Re: bug#25740: [PATCH] Swallow m4traces that have no file/line number

From: Eric Blake <[email-masked]>
Date: Tue, 7 Mar 2017 16:51:46 -0600

autom4te is maintained by autoconf, not automake; redirecting your patch
there.

On 03/07/2017 04:00 PM, Christophe de Dinechin wrote:
> 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+)- ([^(]+)\((.*)$});

Would it be better to keep the error message, but set the file and line
to placeholders, instead of completely discarding the message?

>        # Trace with arguments, as the example above.  We don't try
>        # to match the trailing parenthesis as it might be on a
>        # separate line.
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org