General Protection Violation

ssanyi · #1 (**permalink**) 02-18-04, 03:12

Hi!
I write dll (in c++) for the comunication via serial port. I use Win2000 and Paradox 8 with SP1. Its working whithout problems, but when I exit paradox, I have message "General Protection Violation". Its don't bear whit cominication.

Shores · #2 (**permalink**) 04-21-04, 08:24

When i've tried doing what you're doing, using external DLLs to control serial ports in paradox, i've found that impossible to be reliable, since ObjectPAL doesn't support callback routines, so i reverted to calling directly Win32 APIs from Pdox, and having an hidden form with a timer which polls the port.

If the polling routine is well tuned and only checks for chars in queue with the appropriate win32 call, all will function well and without excessive CPU utilization.

ssanyi · #3 (**permalink**) 04-30-04, 05:31

Hi! Thanks for reply. Can you send me an example program?

Shores · #4 (**permalink**) 04-30-04, 07:01

Sure i can; use the attached library.

Code:

var Comm library endvar
Comm.open("Comm32.lsl")

;open the port
;tmplg1 = Comm.OpenComm(port  ,baud,bits,parity,stopbits)
tmplg1 =  Comm.OpenComm("COM2","96","8" ,"N"   ,"1")

;writing a block of text
tmplg1=Comm.WriteComm(CurrBlock)

;trying to read a block
for tmpli1 from 1 to Maxretry
	sleep()
	if Comm.ReadQueueLen()>0 then
		tmpst1 = fill(" ",NumCharsToRead)
		if Comm.ReadComm(tmpst1) then
			CurrBlock = CurrBlock + tmpst1
		endif
	endif
	sleep()
endfor

ssanyi · #5 (**permalink**) 05-03-04, 09:15

Hello! I try to use Your program, but I have that same GPV message when I exit it. You tested it with Paradox 8, or Paradox 8 Runtime? My algorith for use your program:
1. Open Library
2. Open com
3. n X Write/Read
4. Close Library
...
5.Swearing

Shores · #6 (**permalink**) 05-03-04, 10:13

I suppose you don't close the port...

1)Open lib
2)Open comm
3) Read/write
4)Close comm
5)Close lib

6) No swearing at all...!!!!

ssanyi · #7 (**permalink**) 05-03-04, 10:56

Hi!
I closed the port. But GPW message appears.
Can You send me your paradox forms, or have you any good idea?
Thanks.

Shores · #8 (**permalink**) 05-03-04, 12:52

The only idea i have is that i'm using the library under Pdox 10 SP3 and Windows 2000 SP4...

I don't get no GPF, ever!

ssanyi · #9 (**permalink**) 05-07-04, 03:57

Thanks for answer. Do you know C++ library for read/write data to Paradox tables.

Shores · #10 (**permalink**) 05-20-04, 05:28

No, but i think you can find info about that if you search for BDE infos on Borland's site: the BDE is the db engind Pdox is based on, and surely you can call directly the BD form your C++ apps, directly accessing Pdox tables.

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