[Bug 2960] New: Bug in int 21, function 3f (read) causing WATCOM Win386 Read error

[Wine Bugs]

http://bugs.winehq.org/show_bug.cgi?id=2960

Summary: Bug in int 21, function 3f (read) causing  WATCOM Win386
                    Read error
           Product: Wine
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: wine-dos
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

An old windows 3.1 program (compiled with a watcom compiler) was failing with
the message Read Error in a window called WATCOM Win386. I found the problem was
due to count being set to 0 in int21, function 3f. In my case the
GetSelectorLimit16 was set at 0xffff (DX was set 0) and would make maxcount 0.

Below is a simple fix (making maxcount a double).
in dlls/winedos
--- int21.c.orig        2005-05-13 21:21:32.000000000 -0400
+++ int21.c     2005-05-13 21:24:36.000000000 -0400
@@ -4744,7 +4744,7 @@
             /* Some programs pass a count larger than the allocated buffer */
             if (DOSVM_IsWin16())
             {
-                WORD maxcount = GetSelectorLimit16( context->SegDs )
+                DWORD maxcount = GetSelectorLimit16( context->SegDs )
                     - DX_reg(context) + 1;
                 if (count > maxcount)
                     count = maxcount;