Long and short strings (was: Memory usage stats for 5.2 vs 5.3)

[Dirk Laurie <dirk.laurie@...>]

2015-01-14 14:31 GMT+02:00 Roberto Ierusalimschy <roberto@inf.puc-rio.br>:

> I think we can do that following Tom's idea of storing the length of
> short strings in a byte. Long strings are not hashed, so they do not
> need the 'hnext' field. The struct could look like this:
>
> typedef struct TString {
>   CommonHeader;
>   lu_byte extra;  /* reserved words for short strings; "has hash" for longs */
>   lu_byte shtlen;  /* length for short strings */
>   unsigned int hash;
>   union {
>     size_t len;  /* length for long string */
>     struct TString *hnext;  /* linked list for hash (only for short strings) */
>   } u;
> } TString;

This structure implies that LUAI_MAXSHORTLEN must not be
set to more than 255, right?

The reference manual does not use the phrases 'short string'
and 'long string' nor the word 'internalized', so these must count
as implemetation details.

I'm curious: when a long string is used as a key in a table, will
at that stage the string be internalized?