c++ - how the non-sticky format properties are reseted? -

consider following code:

class c{};  std::ostream &operator <<(std::ostream &o, const c &) {     o.fill('!');     o.width(8);     return o << 42; }  int main() {     std::cout << c{} << '\n';     std::cout << 42 << '\n';     return 0; } 

it outputs:

!!!!!!42

42

i expecting !!!!!!42 twice because i've changed state of provided std::ostream o calling fill , width inside operator <<, used think fill character , width setted operator leak outside operator call if sticky properties.

as can see don't flush stream nor re-set fill character or width so, why (and how) original behaviour preserved?

so question is: how properties of ostream setted previous state after call operator<< class c?

---

this doesn't bothers me, i'm happy behaviour want understand how works.

as underscore_d mentioned: width isn't sticky. there no such attribute stickiness iostream classes , manipulators.

though, if width not have been reset previous << operator call, width affect output of \n:

std::cout << std::setw(10) << std::setfill('!') << 42 << '\n'; std::cout << std::setw(10) << std::setfill('!') << 42 << std::setw(10) << '\n'; 

gives

!!!!!!!!42 !!!!!!!!42!!!!!!!!! 

.