[Sbcl-commits] CVS: sbcl BUGS,1.485,1.486 version.lisp-expr,1.2648,1.2649

[Juho S. <js...@us...>]

Update of /cvsroot/sbcl/sbcl
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv32703

Modified Files:
	BUGS version.lisp-expr 
Log Message:
0.9.8.38:
        Log a BUG.




Index: BUGS
===================================================================
RCS file: /cvsroot/sbcl/sbcl/BUGS,v
retrieving revision 1.485
retrieving revision 1.486
diff -u -d -r1.485 -r1.486
--- BUGS	5 Jan 2006 20:00:39 -0000	1.485
+++ BUGS	13 Jan 2006 11:32:46 -0000	1.486
@@ -2122,3 +2122,31 @@
                                              (force-output)
                                              (sb-ext:gc))))
               (sleep 1))))
+
+398: GC-unsafe SB-ALIEN string deporting
+  Translating a Lisp string to an alien string by taking a SAP to it
+  as done by the :DEPORT-GEN methods for C-STRING and UTF8-STRING
+  is not safe, since the Lisp string can move. For example the
+  following code will fail quickly on both cheneygc and pre-0.9.8.19
+  GENCGC: 
+
+  (setf (bytes-consed-between-gcs) 4096)
+  (define-alien-routine "strcmp" int (s1 c-string) (s2 c-string))
+     
+  (loop
+    (let ((string "hello, world"))
+       (assert (zerop (strcmp string string)))))
+     
+  (This will appear to work on post-0.9.8.19 GENCGC, since
+   the GC no longer zeroes memory immediately after releasing
+   it after a minor GC. Either enabling the READ_PROTECT_FREE_PAGES
+   #define in gencgc.c or modifying the example so that a major
+   GC will occasionally be triggered would unmask the bug.)
+
+  On cheneygc the only solution would seem to be allocating some alien
+  memory, copying the data over, and arranging that it's freed once we
+  return. For GENCGC we could instead try to arrange that the string
+  from which the SAP is taken is always pinned.
+
+  For some more details see comments for (define-alien-type-method
+  (c-string :deport-gen) ...)  in host-c-call.lisp.

Index: version.lisp-expr
===================================================================
RCS file: /cvsroot/sbcl/sbcl/version.lisp-expr,v
retrieving revision 1.2648
retrieving revision 1.2649
diff -u -d -r1.2648 -r1.2649
--- version.lisp-expr	12 Jan 2006 13:26:41 -0000	1.2648
+++ version.lisp-expr	13 Jan 2006 11:32:46 -0000	1.2649
@@ -17,4 +17,4 @@
 ;;; checkins which aren't released. (And occasionally for internal
 ;;; versions, especially for internal versions off the main CVS
 ;;; branch, it gets hairier, e.g. "0.pre7.14.flaky4.13".)
-"0.9.8.37"
+"0.9.8.38"