Make safe_iterator inline friends

[Jonathan Wakely]

On 22/08/18 23:08 +0200, François Dumont wrote:
>Only operator== and != remains outside _Safe_iterator because all my 
>attempts to make them inline friends failed. I understand that an 
>inline friend within a base class is not a very clean design.
>
>Compiler error was:
>
>/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_iterator.h:459: 
>error: redefinition of 'bool __gnu_debug::operator==(const _Self&, 
>const _OtherSelf&)'
>/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_iterator.h:452: 
>note: 'bool __gnu_debug::operator==(const _Self&, const _Self&)' 
>previously declared here
>/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_iterator.h:473: 
>error: redefinition of 'bool __gnu_debug::operator!=(const _Self&, 
>const _OtherSelf&)'
>/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_iterator.h:466: 
>note: 'bool __gnu_debug::operator!=(const _Self&, const _Self&)' 
>previously declared here
>
>I don't know if it is a compiler issue

I don't think so. The error seems clear: when _Self and _OtherSelf are
the same type the friend declarations are the same function.