Tighten close_file, fix SYSLINUX new file APIsyslinux-3.70-pre2

Define close_file slightly tighter:

       - It is permitted to call close_file with a zero filehandle
       - close_file zeros SI

Fix the handling of the new API in SYSLINUX.  It appears file_left was
never actually initialized; it simply didn't matter since the old code
would either trip on reaching the end of the FAT chain or count the
data it needed.  Now operating according to spec.

1 files changed, 1 insertions, 0 deletions

diff --git a/extlinux.asm b/extlinux.asm
index afcdb334..73c8bed5 100644
--- a/extlinux.asm
+++ b/extlinux.asm
@@ -1010,6 +1010,7 @@ close_file:
 		and si,si
 		jz .closed
 		mov dword [si],0		; First dword == file_bytesleft
+		xor si,si
 .closed:	ret
 
 ;