Re: rename LUA_RIDX_CPCALL to LUA_RIDX_CCALL? (5.2.0-work2)
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- Subject: Re: rename LUA_RIDX_CPCALL to LUA_RIDX_CCALL? (5.2.0-work2)
- From: David Manura <dm.lua@...>
- Date: 2010年5月18日 22:51:13 -0400
On Mon, Mar 29, 2010 at 10:22 AM, Roberto Ierusalimschy wrote:
> In 5.2, luaL_cpcall is able to return values. Doesn't that solve
> the problem? (luaL_cpcall is also cheaper than 5.1's lua_cpcall.)
Under Lua 5.2.0work3, we can make this example error safe without too
much trouble:
/* implement common utility function ppushstring (protected push string) */
static int pushudstring(lua_State * L) {
lua_pushstring(L, (char const *)lua_touserdata(L, 1));
return 1;
}
static int ppushstring(lua_State * L, char const * str) {
lua_pushcfunction(L, &pushudstring);
lua_pushlightuserdata(L, str);
return lua_pcall(L, 1, 1, 0);
}
/* now solve the real problem: migrate C heap object to Lua stack object */
char const * const str = some_library_get_string(); /* alloc C
string or return NULL */
int const err = ppushstring(L, str); /* push Lua string (or nil
given NULL) or return error code while pushing Lua error */
some_library_free_string(str);
if (err != 0) lua_error(L);
/* note: Lua string alone exists now */
Perhaps in this case we would prefer this actually:
lua_freezeerror(L); // begin queuing any errors
char const * const str = some_library_get_string();
lua_pushstring(L, str);
some_library_free_string(str);
lua_thawerror(L); // stop queuing errors, clear queue, and raise
first queued error if any