Re: immutable string type

[Bruno Haible <bruno@clisp.org>]

Tim Rühsen wrote on 2019-12-29:
> >> As a more general approach, a function that switches already allocated
> >> memory into read-only memory would be handy. Like in
> >>  - m = malloc()
> >>  - initialize m with some data
> >>  - if in debug mode: call memmap_readonly(m) - from this point on 'm' is
> >> read-only and a write leads to a segmentation fault.
> >>  - ...
> >>  - free(m)
> > 
> > Hardware has write barriers only on the page level. You can't easily request
> > a write barrier for a requence of, say, 30 bytes. To accomodate this, the
> > API needs to have a certain shape. Paul wrote:
> 
> True, and it means that immalloc() always allocate multiples of the page
> size (page is 4096 bytes on x86_64 ?). How do you plan to optimize
> memory usage here ?

I optimized the memory usage by allocated several small or medium sized objects
in a single memory page. Through the module 'ssfmalloc'.

Bruno