Improve commentary for emacs-module.c

* src/lisp.h: Document emacs-module.c assumptions about EQ and NILP.
* src/emacs-module.c (module_non_local_exit_get): Document that we
cannot use the current implementation.
(module_is_not_nil, module_eq): Document assumptions about EQ and
NILP.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/emacs-module.c b/src/emacs-module.c
index ee976440985..5d1b4dc8d6a 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -325,6 +325,8 @@ module_non_local_exit_get (emacs_env *env, emacs_value *sym, emacs_value *data)
   struct emacs_env_private *p = env->private_members;
   if (p->pending_non_local_exit != emacs_funcall_exit_return)
     {
+      /* FIXME: We cannot call lisp_to_value here because that can
+         exit non-locally.  */
       *sym = lisp_to_value (p->non_local_exit_symbol);
       *data = lisp_to_value (p->non_local_exit_data);
     }
@@ -434,6 +436,7 @@ module_is_not_nil (emacs_env *env, emacs_value value)
   check_main_thread ();
   if (module_non_local_exit_check (env) != emacs_funcall_exit_return)
     return false;
+  /* Assume that NILP never exits non-locally.  */
   return ! NILP (value_to_lisp (value));
 }
 
@@ -443,6 +446,7 @@ module_eq (emacs_env *env, emacs_value a, emacs_value b)
   check_main_thread ();
   if (module_non_local_exit_check (env) != emacs_funcall_exit_return)
     return false;
+  /* Assume that EQ never exits non-locally.  */
   return EQ (value_to_lisp (a), value_to_lisp (b));
 }
 
@@ -889,7 +893,7 @@ value_to_lisp_bits (emacs_value v)
 }
 
 /* If V was computed from lisp_to_value (O), then return O.
-   Never fails.  */
+   Must never fail or exit non-locally.  */
 static Lisp_Object
 value_to_lisp (emacs_value v)
 {
@@ -919,7 +923,7 @@ enum { HAVE_STRUCT_ATTRIBUTE_ALIGNED = 0 };
 #endif
 
 /* Convert O to an emacs_value.  Allocate storage if needed; this can
-   signal if memory is exhausted.  */
+   signal if memory is exhausted.  Must be injective.  */
 static emacs_value
 lisp_to_value (Lisp_Object o)
 {