Re: [ANN] Lua 5.4.0 (rc3) now available

[Roberto Ierusalimschy <roberto@...>]

>   typedef struct TString {
>     CommonHeader;
>     lu_byte extra;
>     lu_byte shrlen;
>     unsigned int hash;
>     union {
>       size_t lnglen;
>       struct TString *hnext;
>     } u;
>     char bytes[1];
>   } TString;
> 
>   #define getstr(ts) check_exp(sizeof((ts)->extra), ts->bytes)
> 
>   #define sizelstring(l)  (sizeof(TString) + (l) * sizeof(char))

This code wastes up to seven bytes (due to alignment), compared with
the original version. A better option would be to use 'offsetof' to
compute the size of the rest of the structure:

#define sizelstring(l)  (offsetof(TString, bytes) + ((l) + 1) * sizeof(char))

I hope the new gcc does not complain about that code.

-- Roberto
_______________________________________________
lua-l mailing list -- lua-l@lists.lua.org
To unsubscribe send an email to lua-l-leave@lists.lua.org