Re: Watchpoints for emacs lisp.

[Helmut Eller]

* alin.s [2010-05-15 13:56+0200] writes:

> Suppose that we have the symbol
>
> X = ( 3 . ( 4 . some_cons ) ) 
>
> and
>
> Y = some_cons.
>
> Suppose that I have set the watch bit on X, but not on Y.
>
> In these conditions, modifying Y will not stop into the watchpoint of X.
>
> That means that setting a watchpoint on a symbol X, should be a recursive
> operation, id est, setting recursively a :watch: field for all the
> cons-cells, symbols, strings, etc, which are present in X.
>
> That means that we need to insert a watch field in all lisp data
> strucutures, not only n symbol, etc
>
> Is that algorithm right ?

Can't you use the MMU for this?  Protect the page(s) the watched object
is on; in the SIGSEGV handler set the QUIT flag and store some info in a
global place so that the debugger can figure out which object triggered
the watchpoint.

Helmut