Today, we converted a project from Lua v5.02 to v5.1.1,
and we started having a problem when converting double to
int.
I have narrowed my problem down to code that has nothing
to do with Lua. But I still wanted to get other people's
opinions about it.
double d = 0xFFFFFFFF;
int n;
n = (int)d;
// n now contains 0x80000000
n = (int)(unsigned int)d;
// n now contains 0xFFFFFFFF
(this happens on both VS2005, and GCC 4.0.1 (Apple
Computer, Inc. build 5363))
Since lua_number2int and lua_number2integer both
basically do this: "n = (int)d;"
Wouldn't it be safer to do this: "n = (int)(unsigned
int)d;" so as to preserve the values that would otherwise
be truncated ?
What sort of problems would this cause? Is my fix
unportable?
The initial problem we got stems from doing this in Lua:
d = 0xFFFFFFFF
Foo(d)
// Assuming Foo() is something like this...
int bind_Foo(lua_State *L)
{
Foo(lua_tointeger(L, 1)); // value passed to Foo()
is now
truncated to 0x80000000
return(0);
}
Brian
