Question

I was reading up on this thread on pointer aliasing rules, and one answer gives the following example, which mentions a potential problem with endianness, I wanted to know if anyone could give me what the endianness problem is in the following code?

struct Msg
{
   unsigned int a;
   unsigned int b;
};

int main()
{
   // Pass data to something; if the implementer of this API were
   // strict-aliasing-aware, he would have taken a char*, not a unsigned int*
   Msg* msg = new Msg();
   msg->a = 1;
   msg->b = 2;

   // stupidBuffer is an alias for msg.
   // yes I know there are endianess problems here (WHY??), but my API is stupid and 
   // only works for one platform
   unsigned int* stupidBuffer = reinterpret_cast<unsigned int*>(msg);

   SendToStupidApi( stupidBuffer );   
}

Answer 1

There isn’t any endianness problem. As long as StupidApi doesn’t involve sending it over a network or serialization between platforms, then there’s no endianness issue at all.