C ++ Delete []在VS 2013中给出错误

Question

I am trying to remove a `const char *

int len = str.length();
const char * c = str.c_str();
unsigned short * s = new unsigned short[len];
for (int i = 0; i < len; i++) {
    s[i] = c[i] - '0'; // I dislike this cheat
}


delete[] c; // Gives error.

c is also not used after it is deleted. I am newer to C++ and I am trying to learn the delete operator and it is not going so well :/

Answer 1

I don't support the usage of new and delete in cases like these, but to point out your error, you're deleting memory not allocated via new .

You probably meant to write delete[] s;
(Because s is allocated via new[] )

Also, s could easily be a std::vector<unsigned short> :

// Initializes a vector of unsigned shorts with a specified size.
std::vector<unsigned short> s(len);

Answer 2

const char * c = str.c_str();
delete[] c; // Gives error.

c is a pointer to the contents of str that's still owned and managed by the str object itself, may not be dynamically allocated (eg it could be a pointer to a Short String Optimisation buffer internal to the str object), let alone by new[] , and even if it happens to be the str object will do a delete[] when it goes out of scope or has copied the data to a larger buffer for whatever reason. Summarily, after calling c_str() you can use the pointer until the str object is resized or "destructed", but don't need to do any clean-up yourself.

---

Looking at the rest of your code...

int len = str.length();
const char * c = str.c_str();
unsigned short * s = new unsigned short[len];
for (int i = 0; i < len; i++) {
    s[i] = c[i] - '0'; // I dislike this cheat
}
delete[] c; // Gives error.

...the only error per se is that you delete[] c , but you don't delete[] s and probably should somewhere, some time after it's no longer needed.

That said, you can use std::vector to store the ASCII codes like this (for C++11):

std::vector<unsigned short> s;

for (char c : str)
    s.push_back(c - '0');

If you don't have C++11, then:

for (int i = 0; i < str.length(); ++i)
    s.push_back(c[i] - '0');

...or if you want to try iterators ...

std::vector<unsigned short> s;
for (std::string::const_iterator i = str.begin(); i != str.end(); ++i)
    s.push_back(*i - '0');

You could also use std::copy with an inserter, more declarative but a bit over-the-top IMHO:

std::copy(str.begin(), str.end(), std::back_inserter(s));

Answer 3

No need to delete c, it's only aa pointer to an array (that contains a null-terminated sequence of characters of "str").

The array is still stored in variable "str".