Groups > comp.sys.acorn.programmer > #5455

Re: Filetype list

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From	Harriet Bazley <harriet@bazleyfamily.co.uk>
Newsgroups	comp.sys.acorn.programmer
Subject	Re: Filetype list
Message-ID	<4a5d12f156.harriet@blueyonder.co.uk> (permalink)
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On 30 Apr 2018 as I do recall,
          Martin  wrote:

> On 29 Apr in article <6a1b8ef056.harriet@blueyonder.co.uk>,
>    Harriet Bazley <harriet@bazleyfamily.co.uk> wrote:
> > I've been trying to find out why Textseek's code to generate a list of
> > all available filetypes is crashing on the ARMiniX.
>
> That immediately makes me wonder if it is something peculiar to the
> ARMiniX, not later versions of the OS.
>
> You do not say how it is crashing, or in which line of code, or what OS
> version is being used.

It was crashing in PROCmakemenu at a later stage, when attempting to read
data from a pointer that was pointing into a random memory location and
retrieving a string that was too long for BASIC.
Sometimes (when the random locations are less disastrous) it wasn't
crashing, but was generating a menu with gibberish entries.

>
> > What I've currently got is an attempt to measure the number of filetypes
>
> > DEF FNcountfiletypes
> > LOCAL ptr%,n%,err%
> > REPEAT
> > n%+=1
> > SYS"XOS_ReadVarVal","File$Type_*",wimp%,255,ptr% TO ,,,ptr%;err%
> > UNTIL err% AND 1
> > =n%-1
>
> This does read the variable ... just to check if one exists r2 should be
> negative on entry. I am not sure if checking for an error is the correct
> termination.
>
> Nether the PRM nor StrongHelp manual is clear to me how to terminate a
> wildcarded call. But it seems that r3 is zero when there are no more,
> which seems reasonable.
>
> I suspect r2 can return zero if the variable value is a null string?

i.e. the system variable *exists*, therefore the call returns, but has no
value?

>
> Perhaps the ARMiniX for some reason has a filetype with a null string?

This is what I'm beginning to suspect -- that it's not an OS-specific thing,
but peculiar to that individual machine, and that something I booted is
setting null variables.
(In fact I believe that some of the UNIX ports instruct you to set up null
variables to configure their behaviour, now that I mention it....)

-- 
Harriet Bazley                     ==  Loyaulte me lie ==

Hypocrisy is underrated.

Thread

Filetype list Harriet Bazley <harriet@bazleyfamily.co.uk> - 2018-04-29 23:38 +0100
  Re: Filetype list Martin <News03@avisoft.f9.co.uk> - 2018-04-30 10:54 +0100
    Re: Filetype list Harriet Bazley <harriet@bazleyfamily.co.uk> - 2018-04-30 23:43 +0100
  Re: Filetype list tk@cestriant.plus.com - 2018-04-30 15:12 +0100
  Re: Filetype list Matthew Phillips <spam2011m@yahoo.co.uk> - 2018-05-01 08:31 +0100
    Re: Filetype list Martin <News03@avisoft.f9.co.uk> - 2018-05-01 10:47 +0100
    Re: Filetype list Harriet Bazley <harriet@bazleyfamily.co.uk> - 2018-05-07 23:21 +0100
      Re: Filetype list Harriet Bazley <harriet@bazleyfamily.co.uk> - 2018-05-07 23:37 +0100

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