GNU bug report logs - #35644
emacs module support doesn't work

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Caleb Ristvedt <caleb.ristvedt <at> cune.org>
Subject: bug#35644: closed (Re: bug#35644: emacs module support doesn't work)
Date: Fri, 20 Mar 2020 19:07:02 +0000

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Your bug report

#35644: emacs module support doesn't work

which was filed against the guix package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 35644 <at> debbugs.gnu.org.

-- 
35644: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=35644
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Marius Bakke <mbakke <at> fastmail.com>
To: Caleb Ristvedt <caleb.ristvedt <at> cune.org>, mike <at> rohleder.de
Cc: 35644-done <at> debbugs.gnu.org
Subject: Re: bug#35644: emacs module support doesn't work
Date: Fri, 20 Mar 2020 20:06:17 +0100

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Caleb Ristvedt <caleb.ristvedt <at> cune.org> writes:

> I can confirm that it now works. I did a bit of looking through the commit
> history and playing around with 'guix time-machine', and whatever changed
> to fix
> it, it wasn't a change that touched gnu/packages/emacs.scm. I know it fell
> between 7ab5c4e0e8 and 5ce153b110, though.
>
> Thanks for bringing this up, I guess we can close this now?

Thank you both for the report and investigation.  Closing!

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From: Caleb Ristvedt <caleb.ristvedt <at> cune.org>
To: bug-guix <at> gnu.org
Subject: emacs module support doesn't work
Date: Wed, 08 May 2019 21:16:48 -0500

While attempting to package libegit2
(https://github.com/magit/libegit2), I found that any attempt at loading
a dynamic module from emacs would seemingly work (it returns t), but not
actually work: no module api functions invoked from C seem to have any
effect, including defining functions and printing messages. Here's an
example


-------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <emacs-module.h>

int plugin_is_GPL_compatible;

static emacs_value
hello(emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data)
{
        const char str[] = "Hello Emacs";
        return env->make_string(env, str, sizeof(str) - 1);
}

/* Module init function.  */
int
emacs_module_init(struct emacs_runtime *ert)
{
        emacs_env *env = ert->get_environment(ert);

        emacs_value hellofn = env->make_function(env, 0, 0, hello, "return hello string", NULL);

        // Bind NAME to FUN.
        // (defalias 'hello-c '(lambda () "Hello Emacs"))
        emacs_value defalias_sym = env->intern(env, "defalias");
        emacs_value hello_sym = env->intern(env, "hello-c");
        emacs_value defalias_args[] = { hello_sym, hellofn };

        env->funcall(env, defalias_sym, 2, defalias_args);

        // Provide FEATURE to Emacs.
        // (provide 'hello-core)
        emacs_value feature_sym = env->intern(env, "hello-module");
        emacs_value provide_sym = env->intern(env, "provide");
        emacs_value provide_args[] = { feature_sym };

        env->funcall(env, provide_sym, 1, provide_args);

	char message[] = "TEST MESSAGE!";
	emacs_value message_str = env->make_string(env, message, sizeof(message) - 1);
	emacs_value message_sym = env->intern(env, "message");
	emacs_value message_args[] = {message_str};

	// spam a bit just to be sure
	env->funcall(env, message_sym, 1, message_args);
	env->funcall(env, message_sym, 1, message_args);
	env->funcall(env, message_sym, 1, message_args);

        return 0;
}
-------------------------------

Assuming the above file is named emacs-module-test.c:

-------------------------------
$ gcc -fPIC -shared emacs-module-test.c -o hello-module.so
$ emacs -Q -L . --batch -l hello-module --eval "(message (hello-c))"

=> Symbol's function definition is void: hello-c
-------------------------------

As far as I can tell, this should work. Our emacs is built with
'--with-modules', and 'MODULES' is in system-configuration-features. Any
idea what's going wrong?

- reepca

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