Re: openmpi: FTBFS: Compilation errors

[Eric Blake]

On 08/18/2010 11:31 AM, Ralf Wildenhues wrote:
> [ http://bugs.debian.org/592892 ]
>
> If I got above right, then I'm cloning this bug for Autoconf and
> marking it as upstream bug; adding bug-autoconf in Cc:.
>
> * Sebastian Andrzej Siewior wrote on Wed, Aug 18, 2010 at 04:53:44PM CEST:
> > config/f77_get_alignment.m4.
> > The value should be set in third last line
> >
> > | $2=AS_VAR_GET([type_var])
> >
> > It was transformed earlier into
> > | ofc_type_alignment=$ompi_cv_f77_alignment_LOGICALp1
> > but become something totally differnt,
> >
> > |ofc_type_alignment=`eval 'as_val=${'type_var'};$as_echo "$as_val"'`

The problem here is that the string:

ompi_cv_f77_alignment_LOGICAL*1

is not a shell literal (it contains a globbing character, so unless you 
use it in a quoted context or do the transliteration yourself, we can't 
guarantee that the shell code would be safe).  Meanwhile, AS_LITERAL_IF, 
which forms the backbone of AS_VAR_PUSHDEF, was documented in 2.66 as 
being tightened to be more conservative about what it considers as a 
shell literal.

> Well, AS_VAR_GET is (intentionally) undocumented, so your use of
> AS_VAR_COPY is the right thing to do (which is why I'll leave the
> original bug for openmpi).  Still, this is a regression in upstream
> Autoconf that I think should be fixed.  The issue is that '*' needs to
> be translated to 'p' here and the string treated as literal here:
>
> cat>configure.ac<<\EOF
> AC_DEFUN([OMPI_F77_GET_ALIGNMENT],[
>      AS_VAR_PUSHDEF([type_var], [ompi_cv_f77_alignment_$1])
>      $2=AS_VAR_GET([type_var])

You are correct that using AS_VAR_COPY works around the problem. 
However, you are also correct that autoconf 2.65 would transliterate the 
* at m4 time (treating it as a literal) while 2.66 saves the 
transliteration for shell time (treating it as a variable indirection).

Unfortunately, I don't see any way to make autoconf revert back to the 
2.65 behavior without losing the additional safety that was documented 
in the change for AS_LITERAL_IF being more picky about what forms a 
literal.  So, all I can suggest is that OMPI_F77_GET_ALIGNMENT do the 
transliteration in advance:


AC_DEFUN([OMPI_F77_GET_ALIGNMENT, [
  AS_VAR_PUSHDEF([type_var],
    m4_translit([[ompi_cv_f77_alignment_$1]], [*], [p]))
  AS_VAR_SET([$2], [type_var])

at which point, because you did the transliteration yourself, the 
AS_VAR_PUSHDEF can once again detect that it has a literal at m4 time 
and avoid the extra layer of shell indirection.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org