Re: behaviour of assert on non-string errors
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- Subject: Re: behaviour of assert on non-string errors
- From: Dirk Laurie <dirk.laurie@...>
- Date: 2014年1月17日 18:54:16 +0200
2014年1月17日 Elias Barrionovo <elias.tandel@gmail.com>:
> I always thought assert() called error() internally.
Well, now, this sort of question is not that hard to answer.
Take a look at lbaselib.c.
assert() is very simple indeed.
static int luaB_assert (lua_State *L) {
if (!lua_toboolean(L, 1))
return luaL_error(L, "%s", luaL_optstring(L, 2, "assertion failed!"));
return lua_gettop(L);
}
error() is more sophisticated, because, as the manual states,
| Usually, error adds some information about the error position at
| the beginning of the message, if the message is a string.
static int luaB_error (lua_State *L) {
int level = luaL_optint(L, 2, 1);
lua_settop(L, 1);
if (lua_isstring(L, 1) && level > 0) { /* add extra information? */
luaL_where(L, level);
lua_pushvalue(L, 1);
lua_concat(L, 2);
}
return lua_error(L);
}
So assert() does not call error(). Internally, assert calls luaL_error()
with format string "%s", so the message you supply must have
type string. error calls lua_error() which does not care what type
your message is.