CODEWITHSUNDEEP
c++
zhql0907
zhql0907

Reputation: 369

after delete endl in cout << "hello" << endl, my C++ program stopped working

This is my code. This code can run well. But when I delete "endl" in "cout << "Hello world!" << endl;", It can't run.This is what I get when delete endl

#include <iostream>
#include <cstring>

using namespace std;
int main()
{
    char * name;
    char * n = "aaaa";
    strcpy(name, n);
    cout << name;
    cout << "Hello world!" << endl;
    return 0;
}

The following is the code that deleted endl.

#include <iostream>
#include <cstring>

using namespace std;
int main()
{
    char * name;
    char * n = "aaaa";
    strcpy(name, n);
    cout << name;
    cout << "Hello world!";
    return 0;
}

Upvotes: 0

Views: 548

Answers (4)

Freeze Francis
Freeze Francis

Reputation: 518


char * name;
This line 'name' is not initialised and holds garbage.
Instead do something like:

 using namespace std;
 int main(){

   char name[10];
   char  *n = "aaaa";
   strcpy(name, n);
   cout << name;
   cout << "Hello world!";

   return 0;
}

Upvotes: 1

Quentin
Quentin

Reputation: 63144

name is an uninitialized pointer : it points at some random memory location. When you strcpy to it, you trample five bytes at that location, replacing them with aaaa\0.

Formally, this is undefined behaviour. In practice, you have witnessed two different symptoms : no apparent effect, and a crash.

Point name at a sufficiently large buffer that you actually own, and all will be fine.

Upvotes: 2

Petr Skocik
Petr Skocik

Reputation: 60097

You're copying into a garbage address.

char * name; //<<<garbage address
char * n = "aaaa";
strcpy(name, n);

Upvotes: 0

Some programmer dude
Some programmer dude

Reputation: 409356

Lets take a look at these lines:

char * name;
char * n = "aaaa";
strcpy(name, n);

The variable name is not initialized. It's contents is indeterminate and will be seemingly random. Using it as a destination for a strcpy call will lead to undefined behavior.

If you want to use C-style strings, you need to allocate memory for name, for example by using an array:

char name[128];

But if you are actually programming in C++, why don't you use the awesome classes that comes with the standard library? For example the std::string class that are very good at handling strings:

#include <string>
#include <iostream>

int main()
{
    std::string name;
    std::string n = "aaaa";

    name = n;

    std::cout << name << '\n';
    std::cout << "Hello world" << std::endl;
}

Upvotes: 8

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