Subject: [rohc] operator "!" in the udvm assembly (draft-ietf-rohc-sigcomp-user-guide-01.txt)

From: Cristian CONSTANTIN <[email-masked]>
Date: Mon, 30 May 2005 13:27:25 +0200

hi!

the operator "!" for the udvm assembly language is defined like follows
(excerpt from draft-ietf-rohc-sigcomp-user-guide-01.txt):

"When the symbol "!"
is encountered it is replaced by the location in the bytecode of the
closest DECOMPRESSION-FAILURE instruction (i.e.  the closest zero
byte)."

is there any technique for an udvm assembler
to detect (at "assemble time") the closest zero byte 
to a given address so that this byte is really going to be a
DECOMPRESSION-FAILURE instruction at run time and NOT some data that 
is supposed to be loaded with some other value or some self-modifying 
instruction?

(I'm taking into account here the peculiarities of the udvm code: mixed
data and code, self-modifying code)

bye now!
cristian
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From: Carsten Bormann <[email-masked]>
Date: Mon, 30 May 2005 13:35:46 +0200

Hi Cristian,

> data and code, self-modifying code)

Good point.
No, we did not consider self-modifying code when we defined "!".

Maybe a real-world assembler needs some additional hints here.

Strawman: How about a new set of directives to identify read-only and 
read-write sections?

Gruesse, Carsten