From 3838aeb7397ce80134c70fd49f7e9e5ef7aff3e5 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Sat, 25 Jul 2020 23:23:19 +0200
Subject: [PATCH] Backport: add another test case for module assertions.
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This backports commit 9f01ce6327 from master.  Since the bug isn’t
present on emacs-27, just backport the new test case.

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

* test/src/emacs-module-tests.el
(module--test-assertions--globref-invalid-free): New unit test.
---
 test/data/emacs-module/mod-test.c | 14 ++++++++++++++
 test/src/emacs-module-tests.el    | 11 +++++++++++
 2 files changed, 25 insertions(+)

diff --git a/test/data/emacs-module/mod-test.c b/test/data/emacs-module/mod-test.c
index f6c1c7cf3d2..986c20ae8f9 100644
--- a/test/data/emacs-module/mod-test.c
+++ b/test/data/emacs-module/mod-test.c
@@ -191,7 +191,19 @@ Fmod_test_globref_free (emacs_env *env, ptrdiff_t nargs, emacs_value args[],
   return env->intern (env, "ok");
 }
 
+/* Treat a local reference as global and free it.  Module assertions
+   should detect this case even if a global reference representing the
+   same object also exists.  */
 
+static emacs_value
+Fmod_test_globref_invalid_free (emacs_env *env, ptrdiff_t nargs,
+                                emacs_value *args, void *data)
+{
+  emacs_value local = env->make_integer (env, 9876);
+  env->make_global_ref (env, local);
+  env->free_global_ref (env, local);  /* Not allowed. */
+  return env->intern (env, "nil");
+}
 
 /* Return a copy of the argument string where every 'a' is replaced
    with 'b'.  */
@@ -569,6 +581,8 @@ emacs_module_init (struct emacs_runtime *ert)
 	 1, 1, NULL, NULL);
   DEFUN ("mod-test-globref-make", Fmod_test_globref_make, 0, 0, NULL, NULL);
   DEFUN ("mod-test-globref-free", Fmod_test_globref_free, 4, 4, NULL, NULL);
+  DEFUN ("mod-test-globref-invalid-free", Fmod_test_globref_invalid_free, 0, 0,
+         NULL, NULL);
   DEFUN ("mod-test-string-a-to-b", Fmod_test_string_a_to_b, 1, 1, NULL, NULL);
   DEFUN ("mod-test-userptr-make", Fmod_test_userptr_make, 1, 1, NULL, NULL);
   DEFUN ("mod-test-userptr-get", Fmod_test_userptr_get, 1, 1, NULL, NULL);
diff --git a/test/src/emacs-module-tests.el b/test/src/emacs-module-tests.el
index de707a4243a..e9f13ba368b 100644
--- a/test/src/emacs-module-tests.el
+++ b/test/src/emacs-module-tests.el
@@ -299,6 +299,17 @@ during garbage collection."
     (mod-test-invalid-finalizer)
     (garbage-collect)))
 
+(ert-deftest module--test-assertions--globref-invalid-free ()
+  "Check that -module-assertions detects invalid freeing of a
+local reference."
+    (skip-unless (or (file-executable-p mod-test-emacs)
+                   (and (eq system-type 'windows-nt)
+                        (file-executable-p (concat mod-test-emacs ".exe")))))
+  (module--test-assertion
+      (rx "Global value was not found in list of " (+ digit) " globals")
+    (mod-test-globref-invalid-free)
+    (garbage-collect)))
+
 (ert-deftest module/describe-function-1 ()
   "Check that Bug#30163 is fixed."
   (with-temp-buffer