Dead code in dlls/ntdll/tape.c

[Gerald Pfeifer]

We currently have the following code in tape.c:

if (data->Offset.u.LowPart >= 0) {
            cmd.mt_op = MTFSF;
            cmd.mt_count = data->Offset.u.LowPart;
        }
        else {
            cmd.mt_op = MTBSF;
            cmd.mt_count = -data->Offset.u.LowPart;
        }

data is of type TAPE_SET_POSITION*, which in turn is defined as

typedef struct _TAPE_SET_POSITION {
    ULONG Method;
    ULONG Partition;
    LARGE_INTEGER Offset;
    BOOLEAN Immediate;
  } TAPE_SET_POSITION, *PTAPE_SET_POSITION;

Offset is of type LARGE_INTEGER which is defined as

struct {
        DWORD    LowPart;
        LONG     HighPart;
    } u;

Note how LowPart is unsigned (DWORD) here, so indeed the comparisons
for >= 0 is always going to evaluate to true.

Hans, I believe you originally wrote that code.  Do you remember what
you where trying to do here?

The patch below removes this dead code and is equivalent to what we
currently have.  I am not sure it is the desired way to fix what I
describe above, though.

Gerald

Index: dlls/ntdll/tape.c
===================================================================
RCS file: /home/wine/wine/dlls/ntdll/tape.c,v
retrieving revision 1.16
diff -u -3 -p -r1.16 tape.c
--- dlls/ntdll/tape.c	26 Jun 2007 12:14:34 -0000	1.16
+++ dlls/ntdll/tape.c	1 Nov 2007 16:32:29 -0000
@@ -427,25 +427,13 @@ static NTSTATUS TAPE_SetPosition( int fd
         break;
 #endif
     case TAPE_SPACE_FILEMARKS:
-        if (data->Offset.u.LowPart >= 0) {
-            cmd.mt_op = MTFSF;
-            cmd.mt_count = data->Offset.u.LowPart;
-        }
-        else {
-            cmd.mt_op = MTBSF;
-            cmd.mt_count = -data->Offset.u.LowPart;
-        }
+        cmd.mt_op = MTFSF;
+        cmd.mt_count = data->Offset.u.LowPart;
         break;
 #if defined(MTFSS) && defined(MTBSS)
     case TAPE_SPACE_SETMARKS:
-        if (data->Offset.u.LowPart >= 0) {
-            cmd.mt_op = MTFSS;
-            cmd.mt_count = data->Offset.u.LowPart;
-        }
-        else {
-            cmd.mt_op = MTBSS;
-            cmd.mt_count = -data->Offset.u.LowPart;
-        }
+        cmd.mt_op = MTFSS;
+        cmd.mt_count = data->Offset.u.LowPart;
         break;
 #endif
     case TAPE_LOGICAL_BLOCK: