compiler: better code for global var definitions.

* eval.c (rt_defvarl): More accurate self string.
(rt_defv): New static function: like rt_defvarl but ensures
that the new variable has a binding cell, and returns that
cell instead of the hash cell.
(op_defvarl): Take advantage of rt_defv to not have to cons up
the binding cell.
(eval_init): Register sys:rt-defv intrinsic.

* parser.c (read_file_common): Compiled files are now version
7, so we must recognize them. We still load version 6 files
because rt:defvarl still exists for them.

* share/txr/stdlib/compiler.tl (expand-defvarl): Improve the
generated code in two ways. Firstly, use the new sys:rt-defv,
which returns the binding cell, so that the value can be
stored into it with rplacd without having to cons up anything.
Secondly, if there is no value expression, don't emit the
code to do the assignment.
(%tlo-ver%): Bump compiled file version to (7 0).

* txr.1: Add note about TXR 260 loading version 7 and 6.

1 files changed, 7 insertions, 5 deletions

diff --git a/share/txr/stdlib/compiler.tl b/share/txr/stdlib/compiler.tl
index 2dba0bbe..0e0f3f4f 100644
--- a/share/txr/stdlib/compiler.tl
+++ b/share/txr/stdlib/compiler.tl
@@ -1982,10 +1982,12 @@
 (defun expand-defvarl (form)
   (mac-param-bind form (op sym : value) form
     (with-gensyms (cell)
-      ^(let ((,cell (sys:rt-defvarl ',sym)))
-         (if ,cell
-           (usr:rplacd ,cell (cons ',sym ,value)))
-         ',sym))))
+      (if value
+        ^(let ((,cell (sys:rt-defv ',sym)))
+           (if ,cell
+             (usr:rplacd ,cell ,value))
+           ',sym)
+        ^(progn (sys:rt-defv ',sym) ',sym)))))
 
 (defun expand-defun (form)
   (mac-param-bind form (op name args . body) form
@@ -2164,7 +2166,7 @@
 
 (defvarl %big-endian% (equal (ffi-put 1 (ffi uint32)) #b'00000001'))
 
-(defvarl %tlo-ver% ^(6 0 ,%big-endian%))
+(defvarl %tlo-ver% ^(7 0 ,%big-endian%))
 
 (defvarl %package-manip% '(make-package delete-package
                            use-package unuse-package