Communications (COM1: , COM2:) Receive Buffer Lost During CHAIN (34682)

The information in this article applies to:

Microsoft QuickBASIC 4.0
Microsoft QuickBASIC 4.0b
Microsoft QuickBASIC 4.5
Microsoft BASIC Compiler for MS-DOS and OS/2 6.0
Microsoft BASIC Compiler for MS-DOS and OS/2 6.0b

This article was previously published under Q34682

SYMPTOMS

The communications receive buffer is cleared when chaining to another module; at this point, data can be lost. This problem occurs only in a compiled .EXE program, and does not occur in the QB.EXE editor. Compiling with the BC /d (debug) option does not help. Data received at the communications port after the CHAIN operation is received normally.

STATUS

Microsoft has confirmed this to be a bug in Microsoft QuickBasic Versions 4.00, 4.00b, and 4.50, and in Microsoft Basic Compiler Versions 6.00 and 6.00b for MS-DOS and MS OS/2 (buglist6.00, buglist6.00b). This problem was corrected in Microsoft Basic Professional Development System (PDS) Version 7.00 (fixlist7.00).

MORE INFORMATION

The programs below demonstrate the problem:

    ' File: P1.BAS
   OPEN "com1:1200,e,7,1,cs,ds" FOR RANDOM AS #2
   for x=1 to 10000 :next
   y=loc(2)
   print y;
   CHAIN "p2"    'Chain to second program and print out buffer size


   ' File: P2.BAS
   a$=input$(loc(2),2)
   print a$;


   ' File:P.bas
   'This program will send the characters
   open "com1:1200,e,7,1,cs,ds" for random as #1
   print "start"
   for x=1 to 10000
   print #1, x;
   next x
   close #1

Modification Type:	Minor	Last Reviewed:	1/9/2003
Keywords:	KB34682