Re: LuaJIT FFI simple binding problem

[Pierre Chapuis <catwell@...>]

On 2012-02-21 11:42, Olivier Goudron wrote:

> I am testing LuaJIT FFI binding and i have a problem with this code :
>
> ****
> local ffi = require("ffi")
> ffi.cdef[[
> struct slice{
>   char *data;
>   int len;
> };
> ]]
> local sk = ffi.new("struct slice")
> sk.len = 3
> sk.data = "key"
> print(sk.len)
> print(ffi.string(sk.data))
> ****
> The last line cause LuaJIT to crash and the "sk.data = "key" 
> assignement
> complain with this message : cannot convert 'string' to 'char *'

LuaJIT is telling you what the problem is: you cannot just
assign a Lua string to a char* ctype. You need to allocate
the necessary memory and use ffi.copy.

tl;dr: replace the line:

    sk.data = "key"

by something like:

    sk.data = ffi.new("char[4]")
    ffi.copy(sk.data,"key")

--
Pierre 'catwell' Chapuis