ciface.fs: alter nextprop to preserve output buffer unless an error occurs

Previously nextprop would always write a 0 length string to the output buffer
before calling the underlying property words, with the assumption that this
would be the default return value in the case of an error.

MorphOS breaks this assumption by specifying buf == prev when calling nextprop
which caused the prev value to be overwritten before it could be used, and so
nextprop would always return an (error) exit code of -1.

Fix nextprop so that the 0 length string is only written into the output buffer
when an error exit code of -1 or 0 is returned, as per the IEEE1275
specification. As reported by BALATON Zoltan <balaton@eik.bme.hu>.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

git-svn-id: svn://coreboot.org/openbios/trunk/openbios-devel@1271 f158a5a8-5612-0410-a976-696ce0be7e32

1 files changed, 5 insertions, 3 deletions

diff --git a/forth/system/ciface.fs b/forth/system/ciface.fs
index 5969f4a..727f0a3 100644
--- a/forth/system/ciface.fs
+++ b/forth/system/ciface.fs
@@ -108,12 +108,13 @@ external
   dup 0= if 0 else dup cstrlen then
 
   ( buf prev prev_len )
-  0 3 pick c!
   
   \ verify that prev exists (overkill...)
   dup if
     2dup r@ get-package-property if
-      r> 2drop 2drop -1 exit
+      r> 2drop drop
+      0 swap c!
+      -1 exit
     else
       2drop
     then
@@ -126,7 +127,8 @@ external
     dup 1+ -rot ci-strcpy drop 1
   else
     ( buf )
-    drop 0
+    0 swap c!
+    0
   then
 ;