is portable aliasing possible in C++?

[Andrew Haley]

On 09/15/2014 12:57 PM, Hei Chan wrote:
> // on a big-endian 64-bit machine
> 
> struct Message {
>     int32_t a;
>     int16_t b;
>     char c;
>     char padding;
> };
> 
> // send over a socket
> Message msg = {12345, 678, 'x', 0};

I'd do this:

Message msg = {htonl(12345), htons(678), 'x', 0};

> send(fd, &msg, sizeof Message, 0);
> 
> 
> // another machine: a little-endian 64-bit machine
> char buffer[1024];
> if (recv(fd, buffer, sizeof buffer, 0)) {
>     Message msg;
>     // or we can use the union trick

Why not read into the Message?

>     memcpy(&msg, buffer, sizeof Message);    SomeFunctioToConvertFromBigEndianToSmallEndian(msg.a);

I don't know why you'd want to byte-reverse in place if you actually
care about zero-copy network programming.  That makes no sense to me.

Andrew.