Re: Bug in gnulib-tools prevents bison from bootstrapping

[Hans Aberg]

On 24 Jun 2007, at 04:54, Noah Misch wrote:

> > I have a vague memory that once (?) there was an independent m4, and
> > GNU making their own version gm4. The development of m4 was dropped,
> > so that GNU could take over the name m4.
>
> M4 is a standard tool from the early Unix days; at a minimum, we  
> have the
> original implementation, PD M4, and GNU M4.  Some installers choose  
> to prefix
> GNU program names with `g' on systems that began with non-GNU  
> tools.  There has
> never been a reason to do this on the GNU system, where the GNU  
> program provides
> the principal implementation.
>
> > > The current algorithm is in autoconf's m4/m4.m4:
> > > AC_PATH_PROGS([M4], [gm4 gnum4 m4], [m4])
> > > AC_CACHE_CHECK([whether m4 supports accurate traces],
> > > ...
> > >
> > > In other words, during configuration, autoconf finds the first
> > > program on
> > > your PATH named gm4, gnum4, and then m4, which also meets the  
> > > minimum
> > > requirements of m4 1.4.5 or later.  If you have suggestions for a
> > > better
> > > algorithm, we'd like to know about it.
>
> This sounds like a fine algorithm, but it not the one that the  
> above code
> implements.  Rather, the code finds the first program so-named and  
> checks
> whether that one program meets the version requirement.  It does  
> not continue
> the search upon rejecting a candidate.

The problem is really that the when getting the error, it is hard to  
figure out what is causing it. Without that information, workarounds  
are of little help. This might simplify if the full path of the  
program is written out in the error message.

Another question is to figure out a search method so one does not get  
an error message, except when there actually is no up-to-date GNU M4  
installed. Given the many ways M4 can be configured, the method seems  
to be to search for all three names gm4 gnum4 m4, getting the version  
for each and selecting the most recent GNU M4. If that is not  
sufficiently up-to-date for Autoconf, an error message should be  
issued, with the full paths of the M4 versions it found and examined.

A bit more complicated, but probably not very difficult to implement.

  Hans Aberg