Re: [Bug-apl] Bug: GNU APL does not call start_input after a )LOAD

[Elias Mårtenson]

The problem is not related to the unloading of functions, but that the call to )LOAD triggers a reload of the function, even though the old one is still active.

That reload is what corrupts the Emacs mode in two different ways, either of which would cause the Emacs mode to hang:

• The reload triggers another call to the initialisation code (called by get_signature). This causes an already initialised library to reinitialise. I could deal with this using a flag, but…
• The library that the )LOAD loads is not the same as the one that was originally loaded. In my case, the Emacs native library was original loaded form /home/elias/prog/gnu-apl-mode/native/libemacs.so, but the call to )COPY then loads /home/elias/src/apl/dist/lib/apl/libemacs.so (that's where my development version of GNU APL is installed). So yes, the library is now loaded twice, causing no end of trouble.

Regards,

Elias

On 10 May 2014 21:02, Juergen Sauermann <address@hidden> wrote:

Hi Elias,

I believe this relates to an earlier discussion about removing of callbacks.

Currently a library can decide how it wants to be handled  by )LOAD (actually by )ERASE
which is triggered by )LOAD):

A. be dlcosed() (and then needs to clear/restore its callbacks) or
B. remain loaded.

The default is B as requested earlier (so that the callbacks remain intact). If you
want A. instead then define a function close_fun() and make it return true when called.
Define means that get_function_mux() returns a pointer to it.

Now, if you go for A. then you should restore your callbacks in close_fun().
On the other hand, if you go for B. then you could be called twice and should prepare for that
(a reference counter ++'ed in get_sig() and --'ed in close_fun()). Dito for the same
library used under different names in the same WS, so namespaces would not help).

dlopen() clains to take care of not being loaded twice, but the details are not very clear, eg.
symbolic links to libs, copy of libs etc.

/// Jürgen

On 05/08/2014 03:28 PM, Elias Mårtenson wrote:

OK, thanks for the hints. I've spent some time looking at this issue and I now have an idea what is happening.

When you issue )LOAD, the native library becomes loaded again, even though it's already loaded. There are two issues with this:

First and foremost, after the )LOAD the version of libemacs that is shipped with GNU APL was loaded, not the one correct onw (which happens to be in my development directory). If you intend to call dlopen on the same library, it's important that it's actually the same library and not another one with the same name in a different directory.

Secondly, after loading this library again, GNU APL calls the get_sig() function again. Even if the dlopen() call had returned the same pointer, this would be problematic because the library performs some initialisation stuff in this function call (as you previously had recommended when I asked where I should run the initialisation). Trying to reinitialise an already initialised library is not good.

In short, I think that the idea of using a normal function as entry point into the native code is problematic. I wouldn't mind a redesign of this so that native code lives in a namespace separate from the normal code so it's unaffected by calls to )CLEAR, )ERASE etc.

Regards,

Elias

On 8 May 2014 18:51, Juergen Sauermann <address@hidden> wrote:

Hi,

could you please print the value of start_input  just before line 223 in Input.cc like:

Input::get_user_line(const UCS_string * prompt)
{
Q(start_input)
   if (start_input)   (*start_input)();
...

On my machine it looks OK (even if I don't set it):


     This program is free software, and you are welcome to redistribute it
         according to the GNU Public License (GPL) version 3 or later.
                                      

start_input:         '0' at Input.cc:223
      )load DIJKSTRA
SAVED 2014-5-8  10:42:39 (GMT+2)
start_input:         '0' at Input.cc:223

/// Jürgen

On 05/08/2014 05:07 AM, Elias Mårtenson wrote:

This was reported in this thread: https://github.com/lokedhs/gnu-apl-mode/issues/7

This problem seems to be caused by a bug in GNU APL. When the user calls )LOAD to load a workspace, the start_input callback function is not called before control is returned back to the user.

(because of this, the Emacs mode just sits there, hung, waiting for a call to start_input that never happens).

Regards,

Elias