Ignore pending_signals when checking for quits.

pending_signals is often set if no quit is pending.  This results in
bugs in module code if the module returns but no quit is actually
pending.

As a better alternative, add a new process_input environment function
for Emacs 27.  That function processes signals (like maybe_quit).

* configure.ac: Add module snippet for Emacs 27.

* src/module-env-27.h: New file.

* src/emacs-module.h.in: Add process_input function to environment
interface.

* src/emacs-module.c (module_should_quit): Use QUITP macro to check
whether the caller should quit.
(module_process_input): New function.
(initialize_environment): Use it.

* src/eval.c: Remove obsolete comment.

* test/data/emacs-module/mod-test.c (signal_wrong_type_argument)
(signal_errno): New helper functions.
(Fmod_test_sleep_until): New test module function.

* test/src/emacs-module-tests.el (mod-test-sleep-until): New unit
test.

* doc/lispref/internals.texi (Module Misc): Document process_input.

4 files changed, 37 insertions, 8 deletions

diff --git a/src/emacs-module.c b/src/emacs-module.c
index cbab0234201..b70d6cea812 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -671,13 +671,21 @@ module_vec_size (emacs_env *env, emacs_value vec)
   return ASIZE (lvec);
 }
 
-/* This function should return true if and only if maybe_quit would do
-   anything.  */
+/* This function should return true if and only if maybe_quit would
+   quit.  */
 static bool
 module_should_quit (emacs_env *env)
 {
   MODULE_FUNCTION_BEGIN_NO_CATCH (false);
-  return (! NILP (Vquit_flag) && NILP (Vinhibit_quit)) || pending_signals;
+  return QUITP;
+}
+
+static enum emacs_process_input_result
+module_process_input (emacs_env *env)
+{
+  MODULE_FUNCTION_BEGIN (emacs_process_input_quit);
+  maybe_quit ();
+  return emacs_process_input_continue;
 }
 
 
@@ -1082,6 +1090,7 @@ initialize_environment (emacs_env *env, struct emacs_env_private *priv)
   env->vec_get = module_vec_get;
   env->vec_size = module_vec_size;
   env->should_quit = module_should_quit;
+  env->process_input = module_process_input;
   Vmodule_environments = Fcons (make_mint_ptr (env), Vmodule_environments);
   return env;
 }
diff --git a/src/emacs-module.h.in b/src/emacs-module.h.in
index 4c5286f6257..009d1583fef 100644
--- a/src/emacs-module.h.in
+++ b/src/emacs-module.h.in
@@ -47,7 +47,7 @@ extern "C" {
 #endif
 
 /* Current environment.  */
-typedef struct emacs_env_26 emacs_env;
+typedef struct emacs_env_27 emacs_env;
 
 /* Opaque pointer representing an Emacs Lisp value.
    BEWARE: Do not assume NULL is a valid value!  */
@@ -83,6 +83,16 @@ enum emacs_funcall_exit
   emacs_funcall_exit_throw = 2
 };
 
+/* Possible return values for emacs_env.process_input.  */
+enum emacs_process_input_result
+{
+  /* Module code may continue  */
+  emacs_process_input_continue = 0,
+
+  /* Module code should return control to Emacs as soon as possible.  */
+  emacs_process_input_quit = 1
+};
+
 struct emacs_env_25
 {
 @module_env_snippet_25@
@@ -95,6 +105,15 @@ struct emacs_env_26
 @module_env_snippet_26@
 };
 
+struct emacs_env_27
+{
+@module_env_snippet_25@
+
+@module_env_snippet_26@
+
+@module_env_snippet_27@
+};
+
 /* Every module should define a function as follows.  */
 extern int emacs_module_init (struct emacs_runtime *ert)
   EMACS_NOEXCEPT
diff --git a/src/eval.c b/src/eval.c
index b094fc2e663..b6cdfc911d0 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1575,10 +1575,7 @@ process_quit_flag (void)
    If quit-flag is set to `kill-emacs' the SIGINT handler has received
    a request to exit Emacs when it is safe to do.
 
-   When not quitting, process any pending signals.
-
-   If you change this function, also adapt module_should_quit in
-   emacs-module.c.  */
+   When not quitting, process any pending signals.  */
 
 void
 maybe_quit (void)
diff --git a/src/module-env-27.h b/src/module-env-27.h
new file mode 100644
index 00000000000..b491b60fbbc
--- /dev/null
+++ b/src/module-env-27.h
@@ -0,0 +1,4 @@
+  /* Processes pending input events and returns whether the module
+     function should quit.  */
+  enum emacs_process_input_result (*process_input) (emacs_env *env)
+    EMACS_ATTRIBUTE_NONNULL (1);