getting value of B02 from C

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2 total messages Started by Luigi Semenzato Thu, 27 Aug 1992 00:32

#123

Author: Luigi Semenzato
Date: Thu, 27 Aug 1992 00:32

26 lines
1049 bytes

Easy question:

What's the easiest way of getting the address of the
current stack frame from a C procedure?

One rather unreliable way is the following:

	f()
	{
	    int x[1];
	    int *frame = x - 12;
	    ...
	}

The 12 could be a different number and needs to be
hand-tuned every time the body of f changes.  Bleah.

It would be nice to do it with a call to an assembly
language routine.  But it's not trivial, because there
could be a call to the stack overflow handler between
f and the assembly language routine.

Can it be done using inline assembly with `asm'? 
And if yes, how?

My eternal gratitude in advance.  --Luigi

Re: getting value of B02 from C

#126

Author: Luigi Semenzato
Date: Thu, 27 Aug 1992 17:53

17 lines
866 bytes

Thanks to jjd@teak.cray.com, and others, for the following simple
solution:

         IDENT     GETB02
         ENTRY     GETB02

         SECTION   CODE

GETB02   ENTER     NP=0,MODE=BASELVL
         A5        B02
         S1        A5
         EXIT      MODE=BASELVL

         END

This routine can never cause a stack overflow (it never uses
the stack at all), so my fears where unfounded.  --Luigi

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