c++ - Why Pointer contains some trash? -

i have following code snippet:

size_t size = 5; std::vector<char> container(size, 'd');  std::copy(container.begin(), container.begin() + size,     std::ostream_iterator<char>(std::cout, " ")); // d d d d d  auto ptr = containter.data(); //ptr == dddddtrashtrash why??  char* str_ = new char[size + 1]; memcpy(str_, container.data, size * sizeof(char));  std::cout << str_ << std::endl; // dddddtrashtrashtrash!!!! 

i don't understand, why pointer contains not d. how create pointer 5 symbols of d raii?

because container.data() not null-terminated, pointer doesn't point c-style string. you've put 5 ds there, after bytes unallocated memory. when try stream it, it'll keep going until 1 of unallocated bytes happens \0.

in order print const char* validly, has end \0. can verify with:

size_t size = 5; std::vector<char> container(size, 'd');  container.push_back('\0'); std::cout << container.data(); 

same thing str_. allocated enough memory null-terminator, had add it:

char* str_ = new char[size + 1]; memcpy(str_, container.data, size * sizeof(char)); str_[size] = '\0'; // need