Fix reindent-introduced typo in module code

* src/emacs-module.c (MODULE_SETJMP_1): Fix typo that I
introduced while reindenting the code earlier, and add a
comment explaining the unusual use of do-while here.

1 files changed, 22 insertions, 17 deletions

diff --git a/src/emacs-module.c b/src/emacs-module.c
index 09b09d03366..84072b9917e 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -192,24 +192,29 @@ static void module_wrong_type (emacs_env *, Lisp_Object, Lisp_Object);
 /* It is very important that pushing the handler doesn't itself raise
    a signal.  Install the cleanup only after the handler has been
    pushed.  Use __attribute__ ((cleanup)) to avoid
-   non-local-exit-prone manual cleanup.  */
+   non-local-exit-prone manual cleanup.
+
+   The do-while forces uses of the macro to be followed by a semicolon.
+   This macro cannot enclose its entire body inside a do-while, as the
+   code after the macro may longjmp back into the macro, which means
+   its local variable C must stay live in later code.  */
+
 #define MODULE_SETJMP_1(handlertype, handlerfunc, retval, c, dummy)     \
-  do {                                                                  \
-    eassert (module_non_local_exit_check (env) == emacs_funcall_exit_return); \
-    struct handler *c = push_handler_nosignal (Qt, handlertype);        \
-    if (!c)                                                             \
-      {                                                                 \
-        module_out_of_memory (env);                                     \
-        return retval;                                                  \
-      }                                                                 \
-    verify (module_has_cleanup);                                        \
-    int dummy __attribute__ ((cleanup (module_reset_handlerlist)));     \
-    if (sys_setjmp (c->jmp))                                            \
-      {                                                                 \
-        (handlerfunc) (env, c->val);                                    \
-        return retval;                                                  \
-      }                                                                 \
-  } while (false)
+  eassert (module_non_local_exit_check (env) == emacs_funcall_exit_return); \
+  struct handler *c = push_handler_nosignal (Qt, handlertype);          \
+  if (!c)                                                               \
+    {                                                                   \
+      module_out_of_memory (env);                                       \
+      return retval;                                                    \
+    }                                                                   \
+  verify (module_has_cleanup);                                          \
+  int dummy __attribute__ ((cleanup (module_reset_handlerlist)));       \
+  if (sys_setjmp (c->jmp))                                              \
+    {                                                                   \
+      (handlerfunc) (env, c->val);                                      \
+      return retval;                                                    \
+    }                                                                   \
+  do { } while (false)
 
 
 /* Function environments.  */