Re: Handling for ZLE modules

[Zoltan Hidvegi <hzoli@cs.elte.hu>]

> >deleting at the end.  I have arranged it so that the function is
> >marked as deleted with name "<deleted>" (which should only be used for
> >output), but the table entry is kept.
> 
> I don't like this.  Do we retain the binding or not?  If not, we have

I do not like it either.  A clueless user can have hard time to track down
what changed his keybindings so unexpectedly.

> On a related note, we really need to make addbuiltin() and so on handle
> failure cases gracefully.  Try loading mod_example.so twice ("modload
> ./mod_example.so; modload ~+/mod_example.so"): when I tried it it
> segmentated.  Modules are going to have to cope with the possibility
> that they can't add the builtins, key bindings or whatever that they
> want.

The coredump is caused by the attempt to free the previously defined
builtin in addhashnode().  I think the best is to refuse adding the builtin
if it already exists.  A well behaved module should be prepared to handle
situations when it is loaded multiple times.  The patch below does a
dlclose() and does not add the module to the module list if the boot
function returns nonzero.  Patch to mod_example.c is not included since I'm
writing this from home and the current version is not here with me.

> And if anyone's counting, I, too, favour the name `zmodload'.

That's fine for me.

> (Own up, how many of us are planning how to implement autoloaded modules?)

I am.  We can add a flag to zmodload to define auloaded builtins.  It adds
a builtin with NULL as a handlerfunc.  When such a builtin is executed
execbuiltin() looks up the module with the same name in the MODULE_PATH.
We also have to add some hacks to specify the module which should be loaded
since a package will opten want to define a bunch of builtins which sould
be autoloaded if either one is refered.  The patch below modifies
addbuiltin() so that it allows adding an already defined builtin if its
handler function is NULL.  In that case addbuiltin simply overwrites the
existing structure.  That can be used in the future for autoloading.

Unfortunately it seems to be impossible to handle BINF_MAGICEQUALS and
BINF_PSPECIAL this way (unless we add other options to zmodload for that).

Instead of zmodload it may be better to use the autoload with an option
(e.g. autoload -b).

Zoltan

*** Src/module.c	1996/10/31 01:38:10	3.1.0.1
--- Src/module.c	1996/11/10 23:43:44
***************
*** 159,166 ****
  		    cleanup_module(m);
  		    dlclose(m->handle);
  		    if (! --(m->count)) {
- 			zsfree(m->nam);
  			remnode(modules, node);
  		    }
  		}
  		break;
--- 159,167 ----
  		    cleanup_module(m);
  		    dlclose(m->handle);
  		    if (! --(m->count)) {
  			remnode(modules, node);
+ 			zsfree(m->nam);
+ 			zfree(m, sizeof(*m));
  		    }
  		}
  		break;
***************
*** 175,186 ****
  	    if (! ops['f']) {
  		zwarnnam(nam, "module %s already loaded.", *args, 0);
  		ret++;
! 	    } else if (load_module(*args) != m->handle) {
  		zwarnnam(nam, "reloaded module %s have new handle?", *args, 0);
  		ret++;
  	    } else {
  		m->count++;
- 		ret = init_module(m);
  	    }
  	} else if (! (handle = load_module(*args))) {
  	    zwarnnam(nam, "failed to load module: %s", *args, 0);
--- 176,191 ----
  	    if (! ops['f']) {
  		zwarnnam(nam, "module %s already loaded.", *args, 0);
  		ret++;
! 	    } else if ((handle = load_module(*args)) != m->handle) {
  		zwarnnam(nam, "reloaded module %s have new handle?", *args, 0);
+ 		if (handle)
+ 		    dlclose(handle);
+ 		ret++;
+ 	    } else if (init_module(m)) {
+ 		dlclose(handle);
  		ret++;
  	    } else {
  		m->count++;
  	    }
  	} else if (! (handle = load_module(*args))) {
  	    zwarnnam(nam, "failed to load module: %s", *args, 0);
***************
*** 190,228 ****
  	    m->nam = ztrdup(*args);
  	    m->handle = handle;
  	    m->count = 1;
! 	    PERMALLOC {
! 		addlinknode(modules, m);
! 	    } LASTALLOC;
! 	    ret = init_module(m);
  	}
      }
      return ret;
  }
  
  /**/
! void
  addbuiltin(char *nam, int flags, HandlerFunc hfunc, int minargs, int maxargs, char *optstr)
  {
      Builtin bn;
  
!     bn = zcalloc(sizeof(*bn));
!     bn->nam = nam;
      bn->flags = flags;
      bn->handlerfunc = hfunc;
      bn->minargs = minargs;
      bn->maxargs = maxargs;
      bn->optstr = optstr;
!     PERMALLOC {
! 	builtintab->addnode(builtintab, bn->nam, bn);
!     } LASTALLOC;
  }
  
  /**/
! void
  deletebuiltin(char *nam)
  {
      Builtin bn;
  
      bn = (Builtin) builtintab->removenode(builtintab, nam);
      zfree(bn, sizeof(struct builtin));
  }
--- 195,262 ----
  	    m->nam = ztrdup(*args);
  	    m->handle = handle;
  	    m->count = 1;
! 	    if (init_module(m)) {
! 		dlclose(handle);
! 		ret++;
! 		zsfree(m->nam);
! 		zfree(m, sizeof(*m));
! 	    } else {
! 		PERMALLOC {
! 		    addlinknode(modules, m);
! 		} LASTALLOC;
! 	    }
  	}
      }
      return ret;
  }
  
+ /* addbuiltin() can be used to add a new builtin.  It has six arguments: *
+  *  - the name of the new builtin                                        *
+  *  - BINF_* flags (see zsh.h).  Normally it is 0.                       *
+  *  - the handler function of the builtin                                *
+  *  - minimum number of arguments                                        *
+  *  - maximum number of argument (-1 means unlimited)                    *
+  *  - possible option leters                                             *
+  * It returns zero on succes 1 on failure                                */
+ 
  /**/
! int
  addbuiltin(char *nam, int flags, HandlerFunc hfunc, int minargs, int maxargs, char *optstr)
  {
      Builtin bn;
  
!     bn = (Builtin) builtintab->getnode2(builtintab, nam);
!     if (bn && bn->handlerfunc)
! 	return 1;
!     if (!bn) {
! 	bn = zcalloc(sizeof(*bn));
! 	bn->nam = nam;
! 	PERMALLOC {
! 	    builtintab->addnode(builtintab, bn->nam, bn);
! 	} LASTALLOC;
!     }
      bn->flags = flags;
      bn->handlerfunc = hfunc;
      bn->minargs = minargs;
      bn->maxargs = maxargs;
      bn->optstr = optstr;
!     return 0;
  }
  
+ /* Remove the builtin added previously by addbuiltin().  Returns *
+  * zero on succes and 1 if there is no builtin with that name.   *
+  * Attempt to delete a builtin which is not defined by           *
+  * addbuiltin() will fail badly with unpredictable results.      */
+ 
  /**/
! int
  deletebuiltin(char *nam)
  {
      Builtin bn;
  
      bn = (Builtin) builtintab->removenode(builtintab, nam);
+     if (!bn)
+ 	return 1;
      zfree(bn, sizeof(struct builtin));
+     return 0;
  }