Run Time Error using string pointers

[Joe Speroni]

While playing with pointers, I constructed the following program,
more or less from HELP files, that appears to be correct. When
executed without the MSGBOX statement it terminates without a
problem. No error occurs. When the MSGBOX line is retained, it
seems to provide the correct answer (evidence the program is
correct?), but when the MSGBOX button is clicked a memory
violation error occurs. Is this a compiler bug, or is the
program's use of pointers incorrect.

My PC is a PII system using Windows NT4.0+SP6.
------------------------------------------------------------------
$COMPILE EXE
FUNCTION PBMAIN() AS LONG
DIM R(1:4) AS STRING
R(1)=" String I. ":R(2)=" String II. "
R(3)=" String III. ":R(4)=" String IV. "

DIM xptr(1:4) AS STRING PTR
FOR i&=1 TO 4:xptr(i&)=VARPTR(R(i&)):NEXT

FOR i&=1 TO 4:x$=x$+@xptr(i&)+"|":NEXT
MSGBOX x$ ' without this statement no memory access error occurs
END FUNCTION

[Chuck de Young]

Move the dimension for the pointer and it works, go figure.

$Compile Exe
Option Explicit
Function PbMain() As Long
Dim X As String
Dim I As Long
Dim xPtr(1 To 4) As String Ptr
Dim R(1 To 4) As String

R(1) = " String I. "
R(2) = " String II. "
R(3) = " String III. "
R(4) = " String IV. "

For I = 1 To 4
  xPtr(i) = VarPtr(R(i))
Next

For I = 1 To 4
  X = X & @xPtr(i) & "|"
Next
MsgBox X
End Function

Curious, I hate it when that happens.

Chuck

[Lance Edmonds]

I cannot duplicate Joe's problem with either PB/DLL 5.0 nor PB/DLL 6.0.

Joe, what version of PB/DLL are you using, and what is the date of your PBDLL.EXE file?



-------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Semen Matusovski]

I saw Lance message and decided to test Joe' information (Win98SE, PB/DLL-6).
I started from IDE first time and saw correct data in Msgbox.
Started the second time - GPF. Third time - PC simply had hanged.
I rebooted system and repeat experiment. Approximately the same.

Clear, that happends something not controlled and these statements destroy a memory.

Lance, perhaps, you tested under Win2000 ?

PS. I saw Jim's message. I have IDE Iomega Zip and special driver for electronic keys (LPT)

[This message has been edited by Semen Matusovski (edited January 31, 2000).]

[Jim Padgett]

I get the problem with my PC at work NT SP4 IBM 300XL 128 Meg Ram.
I am running Iomega Parrallel port drivers. I sometimes think they cause
some memory errors. ( I usually get them when the drives are being read
by explorer.
The error on the first program is
The instruction at 0x00000005 referenced memory at 0x00000005.
The memory could not be read.
I don't get this on the second program.
I am running PBDll 6.0.



[This message has been edited by Jim Padgett (edited January 31, 2000).]

[Cecil Williams]

Lance,

I compliled Joe's program in PB/DLL6. Works just fine as you said. I am
using NT4.0 sp6.

Cecil

[Eric Pearson]

The original test program runs repeatedly without errors on my NT4 SP3 system. But it produces an Invalid Page Fault the first time it is run on Windows 98.

-- Eric


-------------
Perfect Sync: Perfect Sync Development Tools
Email: mailto:[email protected][email protected]</A>

[Joe Speroni]

My PBDLL.EXE is dated 7/01/99 201,014 bytes in length.

[K Peel]

Hi,

PBDLL Date: 08.10.1997 (DD.MM.YYYY)
Using windows 98 it produces a page fault GPF.



-------------
Kev G Peel
KGP Software
Bridgwater, UK.
mailto:[email protected][email protected]</A>