lua_number2int

["Brian Weed" <bw@...>]

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