Hi all.
I'd like to take a stab at reimplementing the WindowManager module using
C/C++, in particular to make further development easier and while most of
its SWIs behave "function-like", i.e. return (directly) to their caller, a
few do not, in particular those having to do with creating new tasks and
switching between them, such as Wimp_StartTask and Wimp_Poll.
With CMunge, you define a C/C++ function to be called when a SWI is called,
and when you return from the function, it returns from the SWI, as well.
However, in the case of Wimp_StartTask, the transfer of control is something
like this:
(Current task) -> Wimp_StartTask ("e.g. *SomeWimpTask) (This probably pages
out the "Current task" from &8000, sets up &8000 with the amount of money
specified in the "Next" slot, and issues the command, *SomeWimpTask) ->
SomeWimpTask -> OS_Exit/Wimp_Poll -> Set up original task context and return
from Wimp_StartTask.
This doesn't look like a function call to me... :)
Does anyone have any ideas of how one might implement such SWIs, without
having to do them in ARM assembly, in order to store the return address, set
up context for the new task, etc.?
Regards,
Terje
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