Re: Bad libdir entry in .la files on MSYS/MinGW

[Peter Rosin]

Den 2009-02-04 22:26, skrev Ralf Wildenhues:
> Hi Peter,
>
> * Peter Rosin wrote on Wed, Feb 04, 2009 at 11:11:04AM CET:
> > While playing with func_to_host_path etc by Chuck, I noticed that the
> > libdir entry of installed .la files on MSYS/MinGW contains a path
> > in MSYS format. However, libltdl uses this path to locate the actual
> > module and that will always fail, since MinGW knows nothing about
> > MSYS paths. I think MSYS/MinGW usually gets by without this working
> > since libltdl also checks if the .la file *and* the module itself
> > have been moved, and thus often finds the module relative to where
> > it happened to find the .la file.
> >
> > Attached testcase succeeds on Cygwin and fails on MSYS/MinGW.
> >
> > Is this a sane test? Ok to push?
>
> [...]
> > +# Try finding the module via the libdir entry in a misplaced .la file.
> > +
> > +mv $libdir/a.la $bindir/a.la
>
> Can you explain why this is necessary?  I don't quite understand it,
> given the text above.

If you look in libltdl/ltdl.c:find_module(), you have:

  if (dlname)
    {
      /* try to open the installed module */
      if (installed && libdir)
        {
          if (tryall_dlopen_module (handle, (const char *) 0,
                                    libdir, dlname, advise) == 0)
            return 0;
        }

This tryall_dlopen_module will never succeed on MSYS/MinGW since
'libdir' is an MSYS path, on other hosts it normally succeeds. I
thought this might be a significant difference, and the simplest
way I could think of to tickle it was to separate the .la file from
the .dll file (or .so, whatever). The reason you need to separate
them is that otherwise find_module succeeds later in:

      /* maybe it was moved to another directory */
      {
          if (dir && (tryall_dlopen_module (handle, (const char *) 0,
                                            dir, dlname, advise) == 0))
            return 0;
      }

Where 'dir' is the dir of the .la file (at least I think so).

Hope that clarifies it...

Cheers,
Peter