Re: Watchpoints for emacs lisp.

[Stefan Monnier]

> The block of code that selects a new symbol (in make-symbol) protects the
> shared resource 'symbol_free_list' and the list of blocks for symbol
> allocation (symbol_block) against a concurrent access using the 
> MALLOC_BLOCK_INPUT macro. As far as I know, emacs is only on 1 thread of
> execution.

> In which cases the access to this shared resource is concurrent?

If you build without -DSYNC_INPUT, Emacs may call malloc from
asynchronous signal handlers (yes, it's usually considered as a no-no in
Unix programming, which is why we have switched to SYNC_INPUT).

Another case may have to do with the Gtk build which does use several
threads (tho the extra ones are limited to the Gtk UI part and I'm not
sure if they could interact with this).


        Stefan