Why can't I install libc6-dev-amd64 using the official online repositories?

Question

I'm trying to install libc6-dev-amd64 on my x64 Debian 8 machine.
This is my sources.list file:

deb http://httpredir.debian.org/debian jessie main contrib non-free
deb-src http://httpredir.debian.org/debian jessie main contrib non-free

deb http://httpredir.debian.org/debian jessie-updates main contrib non-free
deb-src http://httpredir.debian.org/debian jessie-updates main contrib non-free

deb http://security.debian.org/ jessie/updates main contrib non-free
deb-src http://security.debian.org/ jessie/updates main contrib non-free

When I try to install libc6-dev-amd64, I get the following error message:

root@debian:~# apt-get update
...
root@debian:~# apt-get install libc6-dev-amd64
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package libc6-dev-amd64

I don't understand why. From what I can tell, the package should be there:
https://packages.debian.org/jessie/libc6-dev-amd64

So how do I fix this?

Answer 1

The libc6-dev-amd64 package is only available on i386. It allows building 64-bit binaries on 32-bit installations. On amd64 systems such as yours, you only need libc6-dev.