Extract check for end of macro to function

* src/macros.h (at_end_of_macro_p):
* src/macros.c (at_end_of_macro_p):
New function.
* src/keyboard.c (read_char): Use the new function.

src/keyboard.c

@@ -2637,8 +2637,7 @@ read_char (int commandflag, Lisp_Object map,
       /* Exit the macro if we are at the end.
 	 Also, some things replace the macro with t
 	 to force an early exit.  */
-      if (EQ (Vexecuting_kbd_macro, Qt)
-	  || executing_kbd_macro_index >= XFIXNAT (Flength (Vexecuting_kbd_macro)))
+      if (at_end_of_macro_p ())
 	{
 	  XSETINT (c, -1);
 	  goto exit;

src/macros.c

@@ -353,6 +353,18 @@ init_macros (void)
   executing_kbd_macro = Qnil;
 }
 
+/* Whether the execution of a macro has reached its end.
+   This should be called only while executing a macro.  */
+
+bool
+at_end_of_macro_p (void)
+{
+  eassume (!NILP (Vexecuting_kbd_macro));
+  /* Some things replace the macro with t to force an early exit.  */
+  return EQ (Vexecuting_kbd_macro, Qt)
+    || executing_kbd_macro_index >= XFIXNAT (Flength (Vexecuting_kbd_macro));
+}
+
 void
 syms_of_macros (void)
 {

src/macros.h

@@ -47,4 +47,9 @@ extern void finalize_kbd_macro_chars (void);
 
 extern void store_kbd_macro_char (Lisp_Object);
 
+/* Whether the execution of a macro has reached its end.
+   This should be called only while executing a macro.  */
+
+extern bool at_end_of_macro_p (void);
+
 #endif /* EMACS_MACROS_H */