C++ - 确定 const char* 是否指向字符串文字或动态对象

Question

void delete_str(const char* theString) {
    // if (theString is pointing to dynamic objects delete it)
        delete[] theString;
    // else do nothing
}

int main() {
    char str[4] = {'a', 'b', 'c', '\0'};

    const char* str0 = "abc"; // assign "abc" to str0
    char* str1 = new char[strlen("abc")+1]; for (int i = 0; i < 4; i++) str1[i] = str[i]; // assign "abc" to str1

    delete_str(str0); // run time error
    delete_str(str1); // ok
}

In this example, I'd like to define a function delete_str() to delete what theString is pointing to. But how could I determine if it points to a string literal or not?

Answer 1

You cannot determine that. The programmer needs to manually keep track of how objects that a pointer points to were created.

That is one of the reasons raw pointers created from new should not be used directly, except in the implementation of a class specifically managing a single such allocation.

Use std::string . You can obtain a null-terminated C string from a std::string using its .c_str() or .data() member functions.

Only use raw pointers as non-owning pointers. Then you will never have to decide whether you need to delete it or not. There are smart pointer such as std::unique_ptr and containers such as std::vector in addition to the std::string class, all of which will handle ownership and correct delete of non-array and array objects for you automatically.