Re: immediate strings

[Andreas Schwab]

Dmitry Antipov <address@hidden> writes:

> @@ -3901,7 +3913,9 @@
>        return (offset >= 0
>             && offset % sizeof b->strings[0] == 0
>             && offset < (STRING_BLOCK_SIZE * sizeof b->strings[0])
> -           && ((struct Lisp_String *) p)->data != NULL);
> +           /* Live immediate string always has at least one
> +              non-zero byte, so this check will be passed.  */
> +           && ((struct Lisp_String *) p)->u.ptrdata != NULL);

Does it?  What about "\0"?

> @@ -843,14 +848,24 @@
>  /* Set text properties.  */
>  #define STRING_SET_INTERVALS(STR, INT) (XSTRING (STR)->intervals = (INT))
>  
> -/* In a string or vector, the sign bit of the `size' is the gc mark bit */
> -
>  struct Lisp_String
>    {
> -    EMACS_INT size;
> -    EMACS_INT size_byte;
> -    INTERVAL intervals;              /* text properties in this string */
> -    unsigned char *data;
> +    EMACS_INT size : BITS_PER_EMACS_INT - 1;
> +    EMACS_INT size_byte : BITS_PER_EMACS_INT - 1;

This means that any access to size or size_byte will have to shift now
(and not just mask) across a word boundary.  This may pessimize it quite
a bit.

Andreas.

-- 
Andreas Schwab, address@hidden
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