Deleting char* after assigning it to a string variable

Question

I have executed the below code and it works perfectly. Since it is about pointers, I just want to be sure. Though I\'m sure that assigning char* to string makes a copy and even

Answer 1

The code is fine, if you look at the constructors of std::basic_string here you'll be able to deduce that std::string has two interesting constructors here:

(4) string(char const*,
           size_type count,
           Allocator const& alloc = Allocator() );

(5) string(char const* s,
           Allocator const& alloc = Allocator() );

Both perform a copy, and the first reads exactly count characters whilst the second reads up until it encounters a NUL-character.

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That being said, I actively encourage you not to use dynamic allocation here. If you want a temporary buffer to play with, consider using std::vector instead.

#include 
#include 
#include 
#include 

int main()
{
    std::string testStr = "whats up ...";
    unsigned strlen = testStr.length();

    std::vector buffer(strlen+1);

    memset(&buffer[0],'\0',strlen+1);
    memcpy(&buffer[0], testStr.c_str(), strlen);

    std::cout << "  :11111111   :   " << &buffer[0] << "\n";

    std::string newStr(&buffer[0]);

    std::cout << "  2222222 : " << newStr << "\n";

    buffer.clear();

    std::cout << "  3333333 : " << newStr << "\n";
}

Note: both vector and string have range-constructors, to build them from a range of iterators, that I purposefully refrained from using to avoid confusion and you being overwhelmed. Just know that you could have used them to avoid calling memcpy and risking a buffer overflow though.