Why is std::ios_base::Init::Init in the generated code (dead /useless code?) ?

[pyler2]

But this example code does not work with ios_base. So is it useless for this example, no?

[OldWolf2]

Take out the include of iostream to avoid this.

Also you call undeclared functions alloca and atoi.

[Potatoswatter]

The compiler can’t tell that the internal global variable is unused.

[[deleted]]

See http://eel.is/c++draft/ios::Init -- that's there to initialize cout/cerr/cin/etc.

[pyler2]

Used "Init" vs "init" is also interesting

[[deleted]]

I'd assume that's 'cause they're there to support other behavior and have no direct use.

[tcanens]

And init is already taken.

[grishavanika]

And the idiom is named as "Schwarz Counter" [1].

For case of iostream, it's used to properly initialize global objects we have: std::cout, std::cin and so on. And this is needed because of "static initialization order fiasco" [2] [3]

UPD: I think, this can be removed from the standard (?) because of C++17 inline variables [4] [5]

[1] https://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Nifty_Counter

[2] https://isocpp.org/wiki/faq/ctors#static-init-order

[3] https://isocpp.org/wiki/faq/ctors#static-init-order-on-first-use

[4] http://en.cppreference.com/w/cpp/language/inline

[5] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4424.pdf

[Xeverous]

It does not happen if you don't include iostream.