Fix subtle bug when checking liveness of module values.

We can't simply look up the Lisp object in the global reference table
because an invalid local and a valid global reference might refer to
the same object.  Instead, we have to test the address of the global
reference against the stored references.

* src/emacs-module.c (module_global_reference_p): New helper function.
(value_to_lisp): Use it.

* test/data/emacs-module/mod-test.c
(Fmod_test_invalid_store_copy): New test module function.
(emacs_module_init): Export it.

* test/src/emacs-module-tests.el
(module--test-assertions--load-non-live-object-with-global-copy):
New unit test.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/data/emacs-module/mod-test.c b/test/data/emacs-module/mod-test.c
index 1e64bcd65f1..437faaee2a0 100644
--- a/test/data/emacs-module/mod-test.c
+++ b/test/data/emacs-module/mod-test.c
@@ -306,6 +306,22 @@ Fmod_test_invalid_load (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
   return invalid_stored_value;
 }
 
+/* The next function works in conjunction with the two previous ones.
+   It stows away a copy of the object created by
+   `Fmod_test_invalid_store' in a global reference.  Module assertions
+   should still detect the invalid load of the local reference.  */
+
+static emacs_value global_copy_of_invalid_stored_value;
+
+static emacs_value
+Fmod_test_invalid_store_copy (emacs_env *env, ptrdiff_t nargs,
+                              emacs_value *args, void *data)
+{
+  emacs_value local = Fmod_test_invalid_store (env, 0, NULL, NULL);
+  return global_copy_of_invalid_stored_value
+         = env->make_global_ref (env, local);
+}
+
 /* An invalid finalizer: Finalizers are run during garbage collection,
    where Lisp code can't be executed.  -module-assertions tests for
    this case.  */
@@ -684,6 +700,8 @@ emacs_module_init (struct emacs_runtime *ert)
   DEFUN ("mod-test-vector-fill", Fmod_test_vector_fill, 2, 2, NULL, NULL);
   DEFUN ("mod-test-vector-eq", Fmod_test_vector_eq, 2, 2, NULL, NULL);
   DEFUN ("mod-test-invalid-store", Fmod_test_invalid_store, 0, 0, NULL, NULL);
+  DEFUN ("mod-test-invalid-store-copy", Fmod_test_invalid_store_copy, 0, 0,
+         NULL, NULL);
   DEFUN ("mod-test-invalid-load", Fmod_test_invalid_load, 0, 0, NULL, NULL);
   DEFUN ("mod-test-invalid-finalizer", Fmod_test_invalid_finalizer, 0, 0,
          NULL, NULL);