Finalizer documentation, minor improvements

* doc/lispref/objects.texi (Finalizer Type): New section
(Type Predicates): Mention finalizers in `type-of' documentation.
* doc/lispref/elisp.texi (Top): Link to finalizer type.

* src/data.c (Ftype_of): Make `type-of' work with finalizers.
(syms_of_data): Register Qfinalizer.

* src/print.c (print_object): Print whether a finalizer has
been called.

* test/automated/finalizer-tests.el (finalizer-object-type): Test that
`type-of' works correctly for finalizers.

doc/lispref/ChangeLog

@@ -1,3 +1,9 @@
+2015-03-03  Daniel Colascione  <dancol@dancol.org>
+
+	* objects.texi (Finalizer Type): New section for finalizer objects.
+	(Type Predicates): Mention finalizers in `type-of' documentation.
+	* elisp.texi (Top): Link to finalizer type.
+
 2015-03-02  Daniel Colascione  <dancol@dancol.org>
 
 	* control.texi (Generators): New section

doc/lispref/elisp.texi

@@ -316,6 +316,7 @@ Programming Types
 * Byte-Code Type::      A function written in Lisp, then compiled.
 * Autoload Type::       A type used for automatically loading seldom-used
                           functions.
+* Finalizer Type::      Runs code when no longer reachable.
 
 Character Type
 

doc/lispref/objects.texi

@@ -156,6 +156,8 @@ latter are unique to Emacs Lisp.
 * Byte-Code Type::      A function written in Lisp, then compiled.
 * Autoload Type::       A type used for automatically loading seldom-used
                         functions.
+* Finalizer Type::      Runs code when no longer reachable.
+
 @end menu
 
 @node Integer Type
@@ -1361,6 +1363,31 @@ in the loaded file.
 @code{autoload}, which stores the object in the function cell of a
 symbol.  @xref{Autoload}, for more details.
 
+@node Finalizer Type
+@subsection Finalizer Type
+
+  A @dfn{finalizer object} helps Lisp code clean up after objects that
+are no longer needed.  A finalizer holds a Lisp function object.
+When a finalizer object becomes unreachable after a garbage collection
+pass, Emacs calls the finalizer's associated function object.
+When deciding whether a finalizer is reachable, Emacs does not count
+references from finalizer objects themselves, allowing you to use
+finalizers without having to worry about accidentally capturing
+references to finalized objects themselves.
+
+Errors in finalizers are printed to @code{*Messages*}.  Emacs runs
+a given finalizer object's associated function exactly once, even
+if that function fails.
+
+@defun make-finalizer function
+Make a finalizer that will run @var{function}.  @var{function} will be
+called after garbage collection when the returned finalizer object
+becomes unreachable.  If the finalizer object is reachable only
+through references from finalizer objects, it does not count as
+reachable for the purpose of deciding whether to run @var{function}.
+@var{function} will be run once per finalizer object.
+@end defun
+
 @node Editing Types
 @section Editing Types
 @cindex editing types
@@ -1907,11 +1934,11 @@ types.  In most cases, it is more convenient to use type predicates than
 This function returns a symbol naming the primitive type of
 @var{object}.  The value is one of the symbols @code{bool-vector},
 @code{buffer}, @code{char-table}, @code{compiled-function},
-@code{cons}, @code{float}, @code{font-entity}, @code{font-object},
-@code{font-spec}, @code{frame}, @code{hash-table}, @code{integer},
-@code{marker}, @code{overlay}, @code{process}, @code{string},
-@code{subr}, @code{symbol}, @code{vector}, @code{window}, or
-@code{window-configuration}.
+@code{cons}, @code{finalizer}, @code{float}, @code{font-entity},
+@code{font-object}, @code{font-spec}, @code{frame}, @code{hash-table},
+@code{integer}, @code{marker}, @code{overlay}, @code{process},
+@code{string}, @code{subr}, @code{symbol}, @code{vector},
+@code{window}, or @code{window-configuration}.
 
 @example
 (type-of 1)

src/ChangeLog

@@ -1,3 +1,11 @@
+2015-03-03  Daniel Colascione  <dancol@dancol.org>
+
+	* print.c (print_object): Print whether a finalizer has
+	been called.
+
+	* data.c (Ftype_of): Make `type-of' work with finalizers.
+	(syms_of_data): Register Qfinalizer.
+
 2015-03-02  Daniel Colascione  <dancol@dancol.org>
 
 	* print.c (print_object): Print finalizers.

src/data.c

@@ -223,7 +223,9 @@ for example, (type-of 1) returns `integer'.  */)
 	case Lisp_Misc_Overlay:
 	  return Qoverlay;
 	case Lisp_Misc_Float:
-	  return Qfloat;
+          return Qfloat;
+        case Lisp_Misc_Finalizer:
+          return Qfinalizer;
 	}
       emacs_abort ();
 
@@ -3547,6 +3549,7 @@ syms_of_data (void)
   DEFSYM (Qcons, "cons");
   DEFSYM (Qmarker, "marker");
   DEFSYM (Qoverlay, "overlay");
+  DEFSYM (Qfinalizer, "finalizer");
   DEFSYM (Qfloat, "float");
   DEFSYM (Qwindow_configuration, "window-configuration");
   DEFSYM (Qprocess, "process");

src/print.c

@@ -2046,7 +2046,10 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
           break;
 
         case Lisp_Misc_Finalizer:
-          strout ("#<finalizer>", -1, -1, printcharfun);
+          strout ("#<finalizer", -1, -1, printcharfun);
+          if (NILP (XFINALIZER (obj)->function))
+            strout (" used", -1, -1, printcharfun);
+          strout (">", -1, -1, printcharfun);
           break;
 
 	  /* Remaining cases shouldn't happen in normal usage, but let's

test/ChangeLog

@@ -1,3 +1,8 @@
+2015-03-03  Daniel Colascione  <dancol@dancol.org>
+
+	* automated/finalizer-tests.el (finalizer-object-type): Test that
+	`type-of' works correctly for finalizers.
+
 2015-03-02  Daniel Colascione  <dancol@dancol.org>
 
 	* automated/generator-tests.el: New tests

test/automated/finalizer-tests.el

@@ -76,3 +76,6 @@
       (should (equal
                (buffer-substring (point) (point-at-eol))
                "finalizer failed: (error \"ABCDEF\")")))))
+
+(ert-deftest finalizer-object-type ()
+  (should (equal (type-of (make-finalizer nil)) 'finalizer)))