Using std Namespace

Question

There seem to be different views on using \'using\' with respect to the std namespace.

Some say use \' using namespace std\', other say don\'t but rathe

Answer 1

Beside to the many correct answers here, I want to state an often forgotten detail: The concept of translation units in C++ seems to be misunderstood by many developers due to common coding and linking schemes. It's common for most of us, that .h files are header files and .cpp files yield the implementation details but that's rather a consent than a strict rule of the standard. How you finally compound your translation units is up to you in doubt.

So for instance with UnityBuilds (linking everything to one single translation unit for speed-up and memory purposes), you can no longer rely on the common consent, that using namespace in .cpp files is quite ok in general. Some might argue, that UnityBuilds circumvent several major C++ core philosophies and are therefore a topic on their own, but nevertheless there are further scenarios where similar issues can occur (local includes in functions for instance). Similar issues arise here with the usage of anonymous namespaces by the way.

Since this was an issue to me in the past, I came up with the "inner guideline" to make things as explicit as possible as long as proportionality allows it.