Question:
what benefits can be derived from such a construction:
namespace{
int i;
}
Answer:
The benefit is the same as using the static — avoiding problems with the one definition rule (ODR) . If, for example, in the title you have int i; , then when connecting to 2 or more .cpp files, you will receive a link error – the same symbol is defined twice. If you write static int i; , then i will become local to every object file that i gets into – i.e. each cpp will have its own i , unlike the first option, where i one for the whole program. The same happens when you write
namespace{
int i;
}
i gets internal linking and therefore there will be no problem with the ODR.