3 files changed, 62 insertions, 4 deletions

diff --git a/test/Makefile.in b/test/Makefile.in
index 7b8c967128f..0c24c48e60e 100644
--- a/test/Makefile.in
+++ b/test/Makefile.in
@@ -68,7 +68,7 @@ EMACS_EXTRAOPT=
 # Command line flags for Emacs.
 # Apparently MSYS bash would convert "-L :" to "-L ;" anyway,
 # but we might as well be explicit.
-EMACSOPT = -batch --no-site-file --no-site-lisp -L "$(SEPCHAR)$(srcdir)" $(EMACS_EXTRAOPT)
+EMACSOPT = -batch --no-site-file --no-site-lisp -module-assertions -L "$(SEPCHAR)$(srcdir)" $(EMACS_EXTRAOPT)
 
 # Prevent any settings in the user environment causing problems.
 unexport EMACSDATA EMACSDOC EMACSPATH GREP_OPTIONS
diff --git a/test/data/emacs-module/mod-test.c b/test/data/emacs-module/mod-test.c
index 309179d1501..fc29a0d6b9a 100644
--- a/test/data/emacs-module/mod-test.c
+++ b/test/data/emacs-module/mod-test.c
@@ -213,6 +213,28 @@ Fmod_test_vector_eq (emacs_env *env, ptrdiff_t nargs, emacs_value args[],
   return env->intern (env, "t");
 }
 
+static emacs_value invalid_stored_value;
+
+/* The next two functions perform a possibly-invalid operation: they
+   store a value in a static variable and load it.  This causes
+   undefined behavior if the environment that the value was created
+   from is no longer live.  The module assertions check for this
+   error.  */
+
+static emacs_value
+Fmod_test_invalid_store (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
+                         void *data)
+{
+  return invalid_stored_value = env->make_integer (env, 123);
+}
+
+static emacs_value
+Fmod_test_invalid_load (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
+                        void *data)
+{
+  return invalid_stored_value;
+}
+
 
 /* Lisp utilities for easier readability (simple wrappers).  */
 
@@ -260,6 +282,8 @@ emacs_module_init (struct emacs_runtime *ert)
   DEFUN ("mod-test-userptr-get", Fmod_test_userptr_get, 1, 1, NULL, NULL);
   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-load", Fmod_test_invalid_load, 0, 0, NULL, NULL);
 
 #undef DEFUN
 
diff --git a/test/src/emacs-module-tests.el b/test/src/emacs-module-tests.el
index 622bbadb3ef..99a853b17e0 100644
--- a/test/src/emacs-module-tests.el
+++ b/test/src/emacs-module-tests.el
@@ -19,9 +19,17 @@
 
 (require 'ert)
 
-(require 'mod-test
-         (expand-file-name "data/emacs-module/mod-test"
-                           (getenv "EMACS_TEST_DIRECTORY")))
+(defconst mod-test-emacs
+  (expand-file-name invocation-name invocation-directory)
+  "File name of the Emacs binary currently running.")
+
+(eval-and-compile
+  (defconst mod-test-file
+    (substitute-in-file-name
+     "$EMACS_TEST_DIRECTORY/data/emacs-module/mod-test")
+    "File name of the module test file."))
+
+(require 'mod-test mod-test-file)
 
 ;;
 ;; Basic tests.
@@ -174,4 +182,30 @@ changes."
   (should (equal (help-function-arglist #'mod-test-sum)
                  '(arg1 arg2))))
 
+(ert-deftest module--test-assertions ()
+  "Check that -module-assertions work."
+  (skip-unless (file-executable-p mod-test-emacs))
+  ;; This doesn’t yet cause undefined behavior.
+  (should (eq (mod-test-invalid-store) 123))
+  (with-temp-buffer
+    (should (equal (call-process mod-test-emacs nil t nil
+                                 "-batch" "-Q" "-module-assertions" "-eval"
+                                 (prin1-to-string
+                                  `(progn
+                                     (require 'mod-test ,mod-test-file)
+                                     ;; Storing and reloading a local
+                                     ;; value causes undefined
+                                     ;; behavior, which should be
+                                     ;; detected by the module
+                                     ;; assertions.
+                                     (mod-test-invalid-store)
+                                     (mod-test-invalid-load))))
+                   ;; FIXME: This string is probably different on
+                   ;; Windows and Linux.
+                   "Abort trap: 6"))
+    (re-search-backward (rx bos "Emacs module assertion: "
+                            "Emacs value not found in "
+                            (+ digit) " values of "
+                            (+ digit) " environments" ?\n eos))))
+
 ;;; emacs-module-tests.el ends here