OpenEuphoria

RE: EXW Crashes!

• Posted by Andy Drummond <kestrelandy at xalt.co.uk> Apr 27, 2001
• 466 views

I'll try the WinDebug, I think, but all bets are off for the weekend as 
I'm tied up (English phrase, don't take it literally). But thanks for 
everyone's help, especially Jonas for telling me that Win32Lib won't 
work with Safe.e - and I use Win32Lib through and through - and yes it 
is WONDERFUL - as is Judith's IDE!!
Andy.

Al Getz wrote:
> Hi there,
> 
> >> I keep getting errors with EXW trying to access 0xffffffff
> 
> Yes, as others had mentioned you are probably trying to poke a 
> value into memory that your code hadnt yet allocated.
> This is something you have to be very strict with.
> 
> You cant allocate 8 bytes and poke 9:
>     atom addr
>     addr=allocate(8)
>     poke(addr,{1,2,3,4,5,6,7,8,9})--triggers error
>     maybe_call_a_function()
>     free(addr)
> 
> A simple way to troubleshoot this kind of problem is
> to insert a few traces into the program such as:
> 
> 1   with trace
> 2   atom addr
> 3   ?1
> 4   trace(1)
> 5   addr=allocate(8)
> 6   poke(addr,{1,2,3,4,5,6,7,8,9})
> 7   maybe_call_a_function()
> 8   free(addr)
> 9   ?2
> 10  trace(1)
> 
> Now when you run the program, it prints a '1' to the screen
> and then starts tracing at the first trace command.
> Now you hit 'Q' and the program crashes BEFORE printing the
> '2', so you know the error occurred between the place where
> the '1' is being printed (line #3) and where the '2'
> is being printed (line #9).
> Now you run the program again only
> this time after the program prints the '1' and starts tracing,
> instead of hitting 'Q' you hit ENTER and trace through
> it line by line.  When you get to the line that causes the error
> and you hit enter, the program crashes.  Now you know the line
> that caused the error at least.  You then have to start
> examining the code up to that point in the program to find
> what may be responsible for the error.  In this example you would
> have to recognize the fact that there are 9 items being 
> poked into successive locations when only 8 have been allocated.
> 
> Sometimes thats the only way to locate an error.
> 
> Oh you could try WinDebug which is on the Euphoria site download
> area, but the procedure is somewhat the same.
<snip>