bug#35644: emacs module support doesn't work

bug#35644: emacs module support doesn't work

[Caleb Ristvedt]

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

bug#35644: emacs module support doesn't work

[mike]

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Caleb Ristvedt <caleb.ristvedt@cune.org> writes:
>
> 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?

I cant reproduce this, it works for me:

$ guix environment -C bash --ad-hoc emacs gcc-toolchain
[env]$ gcc -fPIC -shared emacs-module-test.c -o hello-module.so
[env]$ emacs -Q -L . --batch -l hello-module --eval "(message (hello-c))"  
TEST MESSAGE!
TEST MESSAGE!
TEST MESSAGE!
Hello Emacs


-- 
Der Erfolg ist nicht danach zu beurteilen, was ein Mensch im Leben
erreicht hat, sondern nach den Hindernissen, die er auf dem Weg zum
Erfolg ueberwunden hat.
(Booker T. Washington)

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bug#35644: emacs module support doesn't work

[Caleb Ristvedt]

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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?

- reepca

On Tue, Mar 10, 2020 at 4:52 PM <mike@rohleder.de> wrote:

> Caleb Ristvedt <caleb.ristvedt@cune.org> writes:
> >
> > 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?
>
> I cant reproduce this, it works for me:
>
> $ guix environment -C bash --ad-hoc emacs gcc-toolchain
> [env]$ gcc -fPIC -shared emacs-module-test.c -o hello-module.so
> [env]$ emacs -Q -L . --batch -l hello-module --eval "(message (hello-c))"
> TEST MESSAGE!
> TEST MESSAGE!
> TEST MESSAGE!
> Hello Emacs
>
>
> --
> Der Erfolg ist nicht danach zu beurteilen, was ein Mensch im Leben
> erreicht hat, sondern nach den Hindernissen, die er auf dem Weg zum
> Erfolg ueberwunden hat.
> (Booker T. Washington)
>

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bug#35644: emacs module support doesn't work

[Marius Bakke]

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Caleb Ristvedt <caleb.ristvedt@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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