Trapping I/O runtime errors in GPC_(re)

Tue, 28 Oct 1997 11:53:13 +1100

On 27 Oct 97 at 8:50, Frank Heckenbach wrote:

> I think I can do the RTS part, if you send me a patch for your
> changes, along with a short description about how you did it.

I'll have to sort though my mods to bring them up to date with the 
latest beta.

> 
> I'd imagine I'll do it as follows:
> 
> - Whenever an I/O function encounters an error condition, it sets
> InOutRes to
>   the according error code (which will, of course, *not* be the same
>   as in BP ;-), and return in a clean state. (The latter is the
>   difficult bit; I've already done so for the Read/Write procedures,
>   but I expect there will be more to do so that the program can
>   continue safely.)

That's what I was hoping for.

> 
> - At the start, each I/O function checks InOutRes, and if <>0,
> returns
>   immediately, doing nothing. (Like BP does.)

I hadn't thought of that, but it's an excelent idea.

> 
> - After calling an I/O function, if {$I+} is turned on, the calling
> program
>   must check InOutRes. The code to be generated (perhaps you've
>   already done so) would look like "if InOutRes<>0 then _p_ioerror;"
>   where _p_ioerror will be a RTS function I can provide. (The check
>   "if InOutRes<>0" could also be done in the function (like in BP!),
>   but that's inefficient, because the function has to be called
>   after each I/O operation then.)

Actually, that's almost exactly what my mods do. If IO checking is 
enabled ( {$I+} ), a proceedure taking no parameters is called that 
would check the InOutRes state (though I used a different name) and 
if it's set dumps a dirty message and aborts the program.
Bill
--
Leave others their otherness.

Bill Currie (billc@blackmagic.tait.co.nz)