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Re: A5 in MCL

At 12:17 PM 3/24/94 -0500, Wang Hai wrote:
>Hi, there.
>Does anyone tell me what exactly register A5 means in MCL? Is it a
>special register? What does it do when I call a foreign function? It
>gets passed to the foreign function in #'ff-call.
>Or any suggestions where I can find some information above?

A5 on the Mac is used by most development environments as a
base register for accessing global variables. It is also a base
for the QuickDraw globals. MCL uses it as a base for its subprim
calls. Foreign functions in MCL have their own A5 worlds. Hence,
if you call a foreign function that installs a bunch of traps,
the trap code will likely be run with the wrong value for A5. I have
some code that may help with this if it is your problem. Ask for