Conflate Qnil and Qunbound for `symbol-function'.

* src/alloc.c (Fmake_symbol): Initialize `function' to Qnil.
* src/lread.c (init_obarray): Set `function' fields to Qnil.
* src/eval.c (Fcommandp): Ignore Qunbound.
(Fautoload, eval_sub, Fapply, Ffuncall, Fmacroexpand):
* src/data.c (Ffset, Ffboundp, indirect_function, Findirect_function):
Test NILP rather than Qunbound.
(Ffmakunbound): Set to Qnil.
(Fsymbol_function): Never signal an error.
(Finteractive_form): Ignore Qunbound.

6 files changed, 40 insertions, 27 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9a2cec8a7fc..332656fcf00 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,16 @@
+2012-11-20  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+        Conflate Qnil and Qunbound for `symbol-function'.
+        * alloc.c (Fmake_symbol): Initialize `function' to Qnil.
+        * lread.c (init_obarray): Set `function' fields to Qnil.
+        * eval.c (Fcommandp): Ignore Qunbound.
+        (Fautoload, eval_sub, Fapply, Ffuncall, Fmacroexpand):
+        * data.c (Ffset, Ffboundp, indirect_function, Findirect_function):
+        Test NILP rather than Qunbound.
+        (Ffmakunbound): Set to Qnil.
+        (Fsymbol_function): Never signal an error.
+        (Finteractive_form): Ignore Qunbound.
+
 2012-11-20  Paul Eggert  <eggert@cs.ucla.edu>
 
         * eval.c (interactive_p): Remove no-longer-used decl.
diff --git a/src/alloc.c b/src/alloc.c
index a66a752f5dc..22e3db3cc77 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -3212,7 +3212,7 @@ static struct Lisp_Symbol *symbol_free_list;
 
 DEFUN ("make-symbol", Fmake_symbol, Smake_symbol, 1, 1, 0,
        doc: /* Return a newly allocated uninterned symbol whose name is NAME.
-Its value and function definition are void, and its property list is nil.  */)
+Its value is void, and its function definition and property list are nil.  */)
   (Lisp_Object name)
 {
   register Lisp_Object val;
@@ -3249,7 +3249,7 @@ Its value and function definition are void, and its property list is nil.  */)
   set_symbol_plist (val, Qnil);
   p->redirect = SYMBOL_PLAINVAL;
   SET_SYMBOL_VAL (p, Qunbound);
-  set_symbol_function (val, Qunbound);
+  set_symbol_function (val, Qnil);
   set_symbol_next (val, NULL);
   p->gcmarkbit = 0;
   p->interned = SYMBOL_UNINTERNED;
diff --git a/src/data.c b/src/data.c
index 09899400b68..5fc6afaaa03 100644
--- a/src/data.c
+++ b/src/data.c
@@ -543,12 +543,13 @@ DEFUN ("boundp", Fboundp, Sboundp, 1, 1, 0,
   return (EQ (valcontents, Qunbound) ? Qnil : Qt);
 }
 
+/* FIXME: Make it an alias for function-symbol!  */
 DEFUN ("fboundp", Ffboundp, Sfboundp, 1, 1, 0,
        doc: /* Return t if SYMBOL's function definition is not void.  */)
   (register Lisp_Object symbol)
 {
   CHECK_SYMBOL (symbol);
-  return EQ (XSYMBOL (symbol)->function, Qunbound) ? Qnil : Qt;
+  return NILP (XSYMBOL (symbol)->function) ? Qnil : Qt;
 }
 
 DEFUN ("makunbound", Fmakunbound, Smakunbound, 1, 1, 0,
@@ -564,14 +565,14 @@ Return SYMBOL.  */)
 }
 
 DEFUN ("fmakunbound", Ffmakunbound, Sfmakunbound, 1, 1, 0,
-       doc: /* Make SYMBOL's function definition be void.
+       doc: /* Make SYMBOL's function definition be nil.
 Return SYMBOL.  */)
   (register Lisp_Object symbol)
 {
   CHECK_SYMBOL (symbol);
   if (NILP (symbol) || EQ (symbol, Qt))
     xsignal1 (Qsetting_constant, symbol);
-  set_symbol_function (symbol, Qunbound);
+  set_symbol_function (symbol, Qnil);
   return symbol;
 }
 
@@ -580,9 +581,7 @@ DEFUN ("symbol-function", Fsymbol_function, Ssymbol_function, 1, 1, 0,
   (register Lisp_Object symbol)
 {
   CHECK_SYMBOL (symbol);
-  if (!EQ (XSYMBOL (symbol)->function, Qunbound))
     return XSYMBOL (symbol)->function;
-  xsignal1 (Qvoid_function, symbol);
 }
 
 DEFUN ("symbol-plist", Fsymbol_plist, Ssymbol_plist, 1, 1, 0,
@@ -613,7 +612,7 @@ DEFUN ("fset", Ffset, Sfset, 2, 2, 0,
 
   function = XSYMBOL (symbol)->function;
 
-  if (!NILP (Vautoload_queue) && !EQ (function, Qunbound))
+  if (!NILP (Vautoload_queue) && !NILP (function))
     Vautoload_queue = Fcons (Fcons (symbol, function), Vautoload_queue);
 
   if (AUTOLOADP (function))
@@ -714,7 +713,7 @@ Value, if non-nil, is a list \(interactive SPEC).  */)
 {
   Lisp_Object fun = indirect_function (cmd); /* Check cycles.  */
 
-  if (NILP (fun) || EQ (fun, Qunbound))
+  if (NILP (fun))
     return Qnil;
 
   /* Use an `interactive-form' property if present, analogous to the
@@ -2008,10 +2007,10 @@ indirect_function (register Lisp_Object object)
 
   for (;;)
     {
-      if (!SYMBOLP (hare) || EQ (hare, Qunbound))
+      if (!SYMBOLP (hare) || NILP (hare))
         break;
       hare = XSYMBOL (hare)->function;
-      if (!SYMBOLP (hare) || EQ (hare, Qunbound))
+      if (!SYMBOLP (hare) || NILP (hare))
         break;
       hare = XSYMBOL (hare)->function;
 
@@ -2038,10 +2037,10 @@ function chain of symbols.  */)
 
   /* Optimize for no indirection.  */
   result = object;
-  if (SYMBOLP (result) && !EQ (result, Qunbound)
+  if (SYMBOLP (result) && !NILP (result)
       && (result = XSYMBOL (result)->function, SYMBOLP (result)))
     result = indirect_function (result);
-  if (!EQ (result, Qunbound))
+  if (!NILP (result))
     return result;
 
   if (NILP (noerror))
diff --git a/src/eval.c b/src/eval.c
index 053b1a7f097..34b20f6fc8e 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -875,7 +875,7 @@ definitions to shadow the loaded ones for use in file byte-compilation.  */)
           if (NILP (tem))
             {
               def = XSYMBOL (sym)->function;
-              if (!EQ (def, Qunbound))
+              if (!NILP (def))
                 continue;
             }
           break;
@@ -890,7 +890,7 @@ definitions to shadow the loaded ones for use in file byte-compilation.  */)
           GCPRO1 (form);
           def = Fautoload_do_load (def, sym, Qmacro);
           UNGCPRO;
-          if (EQ (def, Qunbound) || !CONSP (def))
+          if (!CONSP (def))
             /* Not defined or definition not suitable.  */
             break;
           if (!EQ (XCAR (def), Qmacro))
@@ -1715,12 +1715,12 @@ then strings and vectors are not accepted.  */)
 
   fun = function;
 
-  fun = indirect_function (fun); /* Check cycles. */
-  if (NILP (fun) || EQ (fun, Qunbound))
+  fun = indirect_function (fun); /* Check cycles.  */
+  if (NILP (fun))
     return Qnil;
 
   /* Check an `interactive-form' property if present, analogous to the
-     function-documentation property. */
+     function-documentation property.  */
   fun = function;
   while (SYMBOLP (fun))
     {
@@ -1780,7 +1780,7 @@ this does nothing and returns nil.  */)
   CHECK_STRING (file);
 
   /* If function is defined and not as an autoload, don't override.  */
-  if (!EQ (XSYMBOL (function)->function, Qunbound)
+  if (!NILP (XSYMBOL (function)->function)
       && !AUTOLOADP (XSYMBOL (function)->function))
     return Qnil;
 
@@ -1959,7 +1959,7 @@ eval_sub (Lisp_Object form)
 
   /* Optimize for no indirection.  */
   fun = original_fun;
-  if (SYMBOLP (fun) && !EQ (fun, Qunbound)
+  if (SYMBOLP (fun) && !NILP (fun)
       && (fun = XSYMBOL (fun)->function, SYMBOLP (fun)))
     fun = indirect_function (fun);
 
@@ -2081,7 +2081,7 @@ eval_sub (Lisp_Object form)
     val = apply_lambda (fun, original_args);
   else
     {
-      if (EQ (fun, Qunbound))
+      if (NILP (fun))
         xsignal1 (Qvoid_function, original_fun);
       if (!CONSP (fun))
         xsignal1 (Qinvalid_function, original_fun);
@@ -2155,10 +2155,10 @@ usage: (apply FUNCTION &rest ARGUMENTS)  */)
   numargs += nargs - 2;
 
   /* Optimize for no indirection.  */
-  if (SYMBOLP (fun) && !EQ (fun, Qunbound)
+  if (SYMBOLP (fun) && !NILP (fun)
       && (fun = XSYMBOL (fun)->function, SYMBOLP (fun)))
     fun = indirect_function (fun);
-  if (EQ (fun, Qunbound))
+  if (NILP (fun))
     {
       /* Let funcall get the error.  */
       fun = args[0];
@@ -2632,7 +2632,7 @@ usage: (funcall FUNCTION &rest ARGUMENTS)  */)
 
   /* Optimize for no indirection.  */
   fun = original_fun;
-  if (SYMBOLP (fun) && !EQ (fun, Qunbound)
+  if (SYMBOLP (fun) && !NILP (fun)
       && (fun = XSYMBOL (fun)->function, SYMBOLP (fun)))
     fun = indirect_function (fun);
 
@@ -2720,7 +2720,7 @@ usage: (funcall FUNCTION &rest ARGUMENTS)  */)
     val = funcall_lambda (fun, numargs, args + 1);
   else
     {
-      if (EQ (fun, Qunbound))
+      if (NILP (fun))
         xsignal1 (Qvoid_function, original_fun);
       if (!CONSP (fun))
         xsignal1 (Qinvalid_function, original_fun);
diff --git a/src/lisp.h b/src/lisp.h
index 67ae28a488f..4817c6eb990 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1104,7 +1104,7 @@ struct Lisp_Symbol
     union Lisp_Fwd *fwd;
   } val;
 
-  /* Function value of the symbol or Qunbound if not fboundp.  */
+  /* Function value of the symbol or Qnil if not fboundp.  */
   Lisp_Object function;
 
   /* The symbol's property list.  */
diff --git a/src/lread.c b/src/lread.c
index 5859a2f85a9..6d0ff9f780e 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -3957,12 +3957,13 @@ init_obarray (void)
   /* Fmake_symbol inits fields of new symbols with Qunbound and Qnil,
      so those two need to be fixed manually.  */
   SET_SYMBOL_VAL (XSYMBOL (Qunbound), Qunbound);
-  set_symbol_function (Qunbound, Qunbound);
+  set_symbol_function (Qunbound, Qnil);
   set_symbol_plist (Qunbound, Qnil);
   SET_SYMBOL_VAL (XSYMBOL (Qnil), Qnil);
   XSYMBOL (Qnil)->constant = 1;
   XSYMBOL (Qnil)->declared_special = 1;
   set_symbol_plist (Qnil, Qnil);
+  set_symbol_function (Qnil, Qnil);
 
   Qt = intern_c_string ("t");
   SET_SYMBOL_VAL (XSYMBOL (Qt), Qt);