Address of label which is defined within an asm statement?

David Fernandez dfernandez@cct.co.uk
Wed Jun 28 16:00:00 GMT 2006


On Wed, 2006-06-28 at 10:45 -0400, Ioannis E. Venetis wrote:
> Hello Ian,
> 
> Thanks for answering this. I need to access the address of the label 
> within the assembly code that I write. This means that I will have to 
> check again the documentation of this architecture. I hope that I will 
> find something.
> 
> Best regards,
> 
> Ioannis
> 
> > 
> > If you have a label in assembly code, and you want to use it in
> > assembly code, then you need to write whatever is appropriate for your
> > assembly language (e.g., "mov #MyLabel,r0").  That is not really a
> > compiler issue.
> > 
> > If you have a label in assembly code, and you want to use it in C code
> > (e.g., by doing "goto MyLabel;"), then, sorry, you can't do that.
> > 
> > Ian

To obtain the label address could be somthing like "mov #MyLabel, %<n>"
or "mov $MyLabel, %<n>" with <n> the output parameter number where you
get the result like : "=g" (MyLabelAddressVar).

To call a label from C code can be done using
	goto *MyLabelAddressVar
I think that is a C Extension feature of gcc... You cold also pass the
value to another assembler block to do the trick, but that would be
architectural dependent some way...
	"jmp *%0"
	:
	: "r" (MyLabelAddressVar)

David.



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