bug#30373: [PATCH] Implement finalizers for module functions (Bug#30373)

[Philipp Stephani]

* src/module-env-28.h: Add new module environment functions to
module environment for Emacs 28.

* src/emacs-module.c (CHECK_MODULE_FUNCTION): New function.
(struct Lisp_Module_Function): Add finalizer data member.
(module_make_function): Initialize finalizer.
(module_get_function_finalizer)
(module_set_function_finalizer): New module environment functions.
(module_finalize_function): New function.
(initialize_environment): Initialize new environment functions.

* src/alloc.c (cleanup_vector): Call potential module function
finalizer during garbage collection.

* test/data/emacs-module/mod-test.c (signal_error): New helper
function.
(memory_full): Use it.
(finalizer): New example function finalizer.
(Fmod_test_make_function_with_finalizer)
(Fmod_test_function_finalizer_calls): New test module functions.
(emacs_module_init): Define them.

* test/src/emacs-module-tests.el (module/function-finalizer): New unit
test.
---
 src/alloc.c                       |  6 ++++
 src/emacs-module.c                | 45 +++++++++++++++++++++++++---
 src/lisp.h                        |  1 +
 src/module-env-28.h               |  8 +++++
 test/data/emacs-module/mod-test.c | 49 +++++++++++++++++++++++++++++--
 test/src/emacs-module-tests.el    |  8 +++++
 6 files changed, 111 insertions(+), 6 deletions(-)

diff --git a/src/alloc.c b/src/alloc.c
index 6a17bedc75..94c1433124 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -3023,6 +3023,12 @@ cleanup_vector (struct Lisp_Vector *vector)
       if (uptr->finalizer)
        uptr->finalizer (uptr->p);
     }
+  else if (PSEUDOVECTOR_TYPEP (&vector->header, PVEC_MODULE_FUNCTION))
+    {
+      ATTRIBUTE_MAY_ALIAS struct Lisp_Module_Function *function
+        = (struct Lisp_Module_Function *) vector;
+      module_finalize_function (function);
+    }
 }
 
 /* Reclaim space used by unmarked vectors.  */
diff --git a/src/emacs-module.c b/src/emacs-module.c
index ff1a05450c..9ec25d57af 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -122,10 +122,11 @@ Copyright (C) 2015-2019 Free Software Foundation, Inc.
 /* Function prototype for the module init function.  */
 typedef int (*emacs_init_function) (struct emacs_runtime *);
 
-/* Function prototype for module user-pointer finalizers.  These
-   should not throw C++ exceptions, so emacs-module.h declares the
-   corresponding interfaces with EMACS_NOEXCEPT.  There is only C code
-   in this module, though, so this constraint is not enforced here.  */
+/* Function prototype for module user-pointer and function finalizers.
+   These should not throw C++ exceptions, so emacs-module.h declares
+   the corresponding interfaces with EMACS_NOEXCEPT.  There is only C
+   code in this module, though, so this constraint is not enforced
+   here.  */
 typedef void (*emacs_finalizer) (void *);
 
 
@@ -332,6 +333,12 @@ #define MODULE_FUNCTION_BEGIN(error_retval)      \
   MODULE_FUNCTION_BEGIN_NO_CATCH (error_retval); \
   MODULE_HANDLE_NONLOCAL_EXIT (error_retval)
 
+static void
+CHECK_MODULE_FUNCTION (Lisp_Object obj)
+{
+  CHECK_TYPE (MODULE_FUNCTIONP (obj), Qmodule_function_p, obj);
+}
+
 static void
 CHECK_USER_PTR (Lisp_Object obj)
 {
@@ -488,6 +495,7 @@ module_non_local_exit_throw (emacs_env *env, emacs_value 
tag, emacs_value value)
   ptrdiff_t min_arity, max_arity;
   emacs_subr subr;
   void *data;
+  emacs_finalizer finalizer;
 } GCALIGNED_STRUCT;
 
 static struct Lisp_Module_Function *
@@ -521,6 +529,7 @@ module_make_function (emacs_env *env, ptrdiff_t min_arity, 
ptrdiff_t max_arity,
   function->max_arity = max_arity;
   function->subr = func;
   function->data = data;
+  function->finalizer = NULL;
 
   if (docstring)
     function->documentation = build_string_from_utf8 (docstring);
@@ -532,6 +541,32 @@ module_make_function (emacs_env *env, ptrdiff_t min_arity, 
ptrdiff_t max_arity,
   return lisp_to_value (env, result);
 }
 
+static emacs_finalizer
+module_get_function_finalizer (emacs_env *env, emacs_value arg)
+{
+  MODULE_FUNCTION_BEGIN (NULL);
+  Lisp_Object lisp = value_to_lisp (arg);
+  CHECK_MODULE_FUNCTION (lisp);
+  return XMODULE_FUNCTION (lisp)->finalizer;
+}
+
+static void
+module_set_function_finalizer (emacs_env *env, emacs_value arg,
+                               emacs_finalizer fin)
+{
+  MODULE_FUNCTION_BEGIN ();
+  Lisp_Object lisp = value_to_lisp (arg);
+  CHECK_MODULE_FUNCTION (lisp);
+  XMODULE_FUNCTION (lisp)->finalizer = fin;
+}
+
+void
+module_finalize_function (const struct Lisp_Module_Function *func)
+{
+  if (func->finalizer != NULL)
+    func->finalizer (func->data);
+}
+
 static emacs_value
 module_funcall (emacs_env *env, emacs_value func, ptrdiff_t nargs,
                emacs_value *args)
@@ -1339,6 +1374,8 @@ initialize_environment (emacs_env *env, struct 
emacs_env_private *priv)
   env->make_time = module_make_time;
   env->extract_big_integer = module_extract_big_integer;
   env->make_big_integer = module_make_big_integer;
+  env->get_function_finalizer = module_get_function_finalizer;
+  env->set_function_finalizer = module_set_function_finalizer;
   Vmodule_environments = Fcons (make_mint_ptr (env), Vmodule_environments);
   return env;
 }
diff --git a/src/lisp.h b/src/lisp.h
index e0ae2c4262..1bd78284d7 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4245,6 +4245,7 @@ XMODULE_FUNCTION (Lisp_Object o)
   (struct Lisp_Module_Function const *);
 extern module_funcptr module_function_address
   (struct Lisp_Module_Function const *);
+extern void module_finalize_function (const struct Lisp_Module_Function *);
 extern void mark_modules (void);
 extern void init_module_assertions (bool);
 extern void syms_of_module (void);
diff --git a/src/module-env-28.h b/src/module-env-28.h
index dec8704edd..a2479a8f74 100644
--- a/src/module-env-28.h
+++ b/src/module-env-28.h
@@ -1,3 +1,11 @@
   /* Add module environment functions newly added in Emacs 28 here.
      Before Emacs 28 is released, remove this comment and start
      module-env-29.h on the master branch.  */
+
+  void (*(*EMACS_ATTRIBUTE_NONNULL (1)
+            get_function_finalizer) (emacs_env *env,
+                                     emacs_value arg)) (void *) EMACS_NOEXCEPT;
+
+  void (*set_function_finalizer) (emacs_env *env, emacs_value arg,
+                                  void (*fin) (void *) EMACS_NOEXCEPT)
+    EMACS_ATTRIBUTE_NONNULL (1);
diff --git a/test/data/emacs-module/mod-test.c 
b/test/data/emacs-module/mod-test.c
index 5addf61147..6a70a7ab57 100644
--- a/test/data/emacs-module/mod-test.c
+++ b/test/data/emacs-module/mod-test.c
@@ -373,15 +373,20 @@ Fmod_test_add_nanosecond (emacs_env *env, ptrdiff_t 
nargs, emacs_value *args,
 }
 
 static void
-memory_full (emacs_env *env)
+signal_error (emacs_env *env, const char *message)
 {
-  const char *message = "Memory exhausted";
   emacs_value data = env->make_string (env, message, strlen (message));
   env->non_local_exit_signal (env, env->intern (env, "error"),
                               env->funcall (env, env->intern (env, "list"), 1,
                                             &data));
 }
 
+static void
+memory_full (emacs_env *env)
+{
+  signal_error (env, "Memory exhausted");
+}
+
 enum
 {
   max_count = ((SIZE_MAX < PTRDIFF_MAX ? SIZE_MAX : PTRDIFF_MAX)
@@ -490,6 +495,42 @@ Fmod_test_double (emacs_env *env, ptrdiff_t nargs, 
emacs_value *args,
   return result;
 }
 
+static int function_data;
+static int finalizer_calls_with_correct_data;
+static int finalizer_calls_with_incorrect_data;
+
+static void
+finalizer (void *data)
+{
+  if (data == &function_data)
+    ++finalizer_calls_with_correct_data;
+  else
+    ++finalizer_calls_with_incorrect_data;
+}
+
+static emacs_value
+Fmod_test_make_function_with_finalizer (emacs_env *env, ptrdiff_t nargs,
+                                        emacs_value *args, void *data)
+{
+  emacs_value fun
+    = env->make_function (env, 2, 2, Fmod_test_sum, NULL, &function_data);
+  env->set_function_finalizer (env, fun, finalizer);
+  if (env->get_function_finalizer (env, fun) != finalizer)
+    signal_error (env, "Invalid finalizer");
+  return fun;
+}
+
+static emacs_value
+Fmod_test_function_finalizer_calls (emacs_env *env, ptrdiff_t nargs,
+                                    emacs_value *args, void *data)
+{
+  emacs_value Flist = env->intern (env, "list");
+  emacs_value list_args[]
+    = {env->make_integer (env, finalizer_calls_with_correct_data),
+       env->make_integer (env, finalizer_calls_with_incorrect_data)};
+  return env->funcall (env, Flist, 2, list_args);
+}
+
 /* Lisp utilities for easier readability (simple wrappers).  */
 
 /* Provide FEATURE to Emacs.  */
@@ -566,6 +607,10 @@ #define DEFUN(lsym, csym, amin, amax, doc, data) \
   DEFUN ("mod-test-add-nanosecond", Fmod_test_add_nanosecond, 1, 1, NULL, 
NULL);
   DEFUN ("mod-test-nanoseconds", Fmod_test_nanoseconds, 1, 1, NULL, NULL);
   DEFUN ("mod-test-double", Fmod_test_double, 1, 1, NULL, NULL);
+  DEFUN ("mod-test-make-function-with-finalizer",
+         Fmod_test_make_function_with_finalizer, 0, 0, NULL, NULL);
+  DEFUN ("mod-test-function-finalizer-calls",
+         Fmod_test_function_finalizer_calls, 0, 0, NULL, NULL);
 
 #undef DEFUN
 
diff --git a/test/src/emacs-module-tests.el b/test/src/emacs-module-tests.el
index 322500ff60..d9a57aecf6 100644
--- a/test/src/emacs-module-tests.el
+++ b/test/src/emacs-module-tests.el
@@ -402,4 +402,12 @@ module-darwin-secondary-suffix
         (load so nil nil :nosuffix :must-suffix)
       (delete-file so))))
 
+(ert-deftest module/function-finalizer ()
+  (mod-test-make-function-with-finalizer)
+  (let* ((previous-calls (mod-test-function-finalizer-calls))
+         (expected-calls (copy-sequence previous-calls)))
+    (cl-incf (car expected-calls))
+    (garbage-collect)
+    (should (equal (mod-test-function-finalizer-calls) expected-calls))))
+
 ;;; emacs-module-tests.el ends here
-- 
2.21.0 (Apple Git-122.2)