26bit BorderUtil issue

BorderUtil can generate an Address Exception under RO 3.1×. The problem has been around since day 1 as its a programming issue. The repro in my case is:

1. Ensure !Boot.Resources.!System.310.Modules.Wimp exists and the ROM version of WindowManager is 3.16 (ie RO 3.10 or RO 3.11)
2. Boot normally
3. CTRL-SHIFT-F12 twice
4. *Desktop
5. CTRL-SHIFT-F12

BorderUtils then Aborts at the LDR LR,[R1,#w_taskhandle] instruction.

BorderUtils is redundant with an updated WindowManager so the issue is its failure to unload or cease functioning once the updated Wimp Module is loaded by !Boot.

Possible solutions for PlingSystem:

1. Replace BorderUtils with a stub Module that does nothing
2. Change !Boot to load BorderUtils last
3. Change !Boot to not load BorderUtils if its going to load Wimp
4. Change the Service handler in BorderUtils to detect if WindowManager has changed

The workaround is simple enough – just delete BorderUtils from !Boot, but its probable a good idea not to distribute a !SysMerge that’s going to definitely cause problems.

I’ll see if I can come up with something sensible to cover option 4.

BorderUtils is redundant with an updated WindowManager so the issue is its failure to unload or cease functioning once the updated Wimp Module is loaded by !Boot.

Boot already kills off BorderUtils when the Wimp is loaded since as far back as May 2013, but it looks like a copy paste fumble means that on RISC OS 3.10 it’s skipped.

Change the line in PreDesktop from

If Boot$OSVersion < 350 Then X RMKill BorderUtils

X RMKill BorderUtils

PlingSystem doesn’t update PreDesktop and that line wasn’t in mine. As a temp fix I put an Obey in PreDesk to kill it if anything other than WindowManager 3.16 is loaded:

SetEval kill$borderutils 1
RMEnsure WindowManager 3.17 SetEval kill$borderutils 0
RMEnsure WindowManager 3.16 SetEval kill$borderutils 1
IF kill$borderutils THEN RMKill BorderUtils
UnSet kill$borderutils

Updating BorderUtils to check the WindowManager version when the Wimp starts is probably a better solution as there’s no external reliance to kill it.