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Q30393: Parameters Incorrectly Passed in Nested Subprogram CALLs

Article: Q30393
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b fixlist4.50 B_BasicCom | mspl13_basic
Last Modified: 22-JAN-1990

When making nested subprogram CALLs, the parameters passed in the CALL
statements get mixed up in the example program below if they are
compiled with BC.EXE from QuickBASIC Version 4.00. The program works
correctly when run in the QB.EXE interpreter.

Microsoft has confirmed this to be a problem in QuickBASIC Versions
4.00 and 4.00b 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 QuickBASIC Version 4.50 and in Microsoft BASIC
Professional Development System (PDS) Version 7.00 for MS-DOS and MS
OS/2 (fixlist7.00).

This problem does not occur in QuickBASIC Version 3.00.

The program below improperly passes the first parameter into the
second parameter on the third nested CALL.

The assembly listing (generated with the BC.EXE /A option) for the
following sample program demonstrates that inside the SUB, the SI
register is pushed twice onto the stack without being reset.

When the sample program below is compiled without the debug (/d)
option, the output from the EXE program is incorrect (you get the
value -999 rather than 1).

If compiled with the debug option, the run-time error message
"Subscript out of range" appears after printing the first two lines of
output.

The program runs correctly if line numbers are added to the "subp3"
subprogram and the program is then compiled with the debug option.

The following is a sample program:

' The main program and three subprograms are contained in one source
file:
DEFINT A-Z
CONST cnst1 = 40
        '  ARRAY DIMENSIONING
DIM array2(cnst1), array1(cnst1)
COMMON SHARED array2(), array1()
d1$ = ""
d2 = -999
fi = 1
PRINT "file.index = "; fi
CALL subp1(d1$, d2, fi)

SUB subp1 (dummy1$, dummy2, dummy3) STATIC  ' dummy3 = fi (file.index)
dummy1$ = ""
CALL subp3(dummy3)
v1 = LOF(array2(dummy3)) / 2
IF v1 >= dummy2 THEN
  array1(dummy3) = dummy2
  CALL subp2(dummy3)
END IF
END SUB

SUB subp2 (dummy4) STATIC         ' dummy4 = dummy3 = fi (file.index)
PRINT "Sub2. file.index = "; dummy4
END
END SUB

SUB subp3 (dummy5) STATIC         ' dummy5 = dummy3 = fi (file.index)
OPEN "r", dummy5, "dummy.fil", 128
array2(dummy5) = dummy5
PRINT "Sub3. file.index = "; dummy5
END SUB

'Output from editor:                    Output from EXE (without /d):

' file.index = 1                                file.index = 1
' Sub3. file.index = 1                  Sub3. file.index = 1
' Sub2. file.index = 1                  Sub2. file.index = -999

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