Copying a std::string to char*

Question

I am trying to create a copy of a std::string to a char*. This is my function and its seen result:

void main()
{
std::string test1;
std::cout << "Enter Data1" << std::endl;
std::cin >> test1;
char* test2;
test2 = (char*)test1.c_str();
std::cout << "test1: "<< &test1 << std::endl;
std::cout << "test2: "<< &test2 << std::endl;
}

Enter Data1
Check
test1: 0x7fff81d26900
test2: 0x7fff81d26908

I am unsure if a copy has been created or both of them are pointing to the same location. How to confirm this?

Please be noted, test1 is a class, test2 is a pointer, it's totally different. test1.c_str() return the pointer of the member of test1. Alexis's answer is correct way to copy whole data to a new pointer. — Yigang Wu, Jul 31 '13 at 06:05

score 2 · Accepted Answer · edited Jun 10 '18 at 23:19

2

You are just copying the adress and using a C cast in C++ use strdup instead

char* test2;
test2 = strdup(test1.c_str()); //free it after

or

   char *test2 = malloc(test1.size());
   strcpy(test2, test1.c_str());

edited Jun 10 '18 at 23:19

Marc J. Schmidt

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answered Jul 31 '13 at 06:01

Alexis

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1

Not a standard function. Anyway this is a duplicate and has been answered before. – Rapptz Jul 31 '13 at 06:04
1

Your edit is wrong. Also in C++ we use `new`, `delete` and `std::copy` not `malloc`, `free`, and `strcpy`. – Rapptz Jul 31 '13 at 06:09
1

yeah and you don't use char* but vector of char, string or any objects, but the question is about char* – Alexis Jul 31 '13 at 06:11
How can you use c_str as size for malloc? – huysentruitw Jul 31 '13 at 06:12
@WouterHuysentruit sorry forgot the strlen, edited now – Alexis Jul 31 '13 at 06:13
2

Seriously, `strlen`? Do you realise the string already knows its own size? – R. Martinho Fernandes Jul 31 '13 at 06:47

Copying a std::string to char*

1 Answers1