Re: ltdl.c and 1.4.1 (type conflicts)

[Gary V. Vaughan]

On Sat, Sep 08, 2001 at 01:49:35AM -0700, Bruce Korb wrote:
> Robert Collins wrote:
> > 
> > On Sat, 2001-09-08 at 13:31, Gary V. Vaughan wrote:
> > > On Fri, Sep 07, 2001 at 02:45:11PM -0500, Tim Mooney wrote:
> > > Phew!  Thanks for that info.
> > >
> > > I'm open to suggestions for a cleaner way to implement this, but I
> > > think that it is an unavoidable weakness in C that forces one to (ab)use
> > > void* in cases such as this.
> > 
> > I haven't checked the code in question, but if what youa re doing is
> > returning a pointer to a function froma function, then typdef'ing a
> > function pointer type and returning that should be a clean solution.
> > 
> > ie if the function type being passed around is
> > int func(char *, int)
> > 
> > typedef int functype(char *, int);
> > 
> > functype *
> > functionthatreturnspointertofunction()
> > {
> >  ...
> > }
> 
> That's my preferred solution, too.  Unfortunately, libtool is _still_
> trying to be K&R compatible, and ancient K&R won't let you typedef
> procedures.

I didn't know that... pfff. :-P

Anyway, would that it were so easy.  foreach_dirinpath is a general
helper function used in all sorts of contexts throughout ltdl.c:

typedef int     foreach_callback_func LT_PARAMS((char *filename, lt_ptr data1,
                                                 lt_ptr data2));

static int
foreach_dirinpath (search_path, base_name, func, data1, data2)
     const char *search_path;
     const char *base_name;
     foreach_callback_func *func;
     lt_ptr data1;
     lt_ptr data2;
{
  ...
}


This is an API call, implemented over foreach_dirinpath:

int
lt_dlforeachfile (search_path, func, data)
     const char *search_path;
     int (*func) LT_PARAMS ((const char *filename, lt_ptr data));
     lt_ptr data;
{
  ...
  if (search_path)
    {
      /* If a specific path was passed, search only the directories
         listed in it.  */
      is_done = foreach_dirinpath (search_path, 0,
                                   foreachfile_callback, func, data);
    }
  ...
}


This function has to match the foreach_callback_func footprint, so
that it can be passed to foreach_dirinpath, but it also needs to accept
a function pointer itself to work with lt_dlforeachfile:

static int
foreachfile_callback (dirname, data1, data2)
     char *dirname;
     lt_ptr data1;
     lt_ptr data2;
{

  int (*func) LT_PARAMS((const char *filename, lt_ptr data))
        = (int (*) LT_PARAMS((const char *filename, lt_ptr data))) data1;
  ^^^^^^ Here is one of the casts xlc dislikes ^^^^^
  ...
  {
     char *filename = 0;
     while ((filename = argz_next (argz, argz_len, filename)))
       if ((is_done = (*func) (filename, data2)))
         break;
  }                       }
  ...                     
}

Suggestions?

Cheers,
        Gary.          
-- 
  ())_. Gary V. Vaughan     gary@(oranda.demon.co.uk|gnu.org)
  ( '/  Research Scientist  http://www.oranda.demon.co.uk       ,_())____
  / )=  GNU Hacker          http://www.gnu.org/software/libtool  \'      `&
`(_~)_  Tech' Author        http://sources.redhat.com/autobook   =`---d__/