How do I update C++ to C11 on Ubuntu 14.10?

Question

How can I upgrade the version of C++ to C11?

Details:

• Ubuntu 14.10 32b
• GCC 4.9.1 (Ubuntu 4.9.1-16ubuntu6)

Answer 1

In your specific situation there is nothing to be updated. As this your comment you use the version GCC 4.9.1, that supports the standard C11.

According to the GCC Wiki:

GCC 4.9 Changes: "ISO C11 support is now at a level similar to ISO C99 support.."

Basically you have to change the function itoa for std::to_string.

The real problem is using the function itoa, it is not a standard function and does not work on GCC on Linux (at least in my case). A minimum, complete and verifiable example of this problem may be:

#include <stdio.h>
#include <stdlib.h>

int main (){
  int i;
  char buffer [10];
  printf ("Digite um número: ");
  scanf ("%d", &i);
  itoa (i, buffer, 10);
  printf ("String: %s\n", buffer);
  return 0;
}

When compiling, the following message will appear:

$ g++ -std=c++11 main.cpp -o exemplo1
main.cpp: In function ‘int main()’:
main.cpp:9:22: error: ‘itoa’ was not declared in this scope
   itoa (i, buffer, 10);
                      ^
$

Note: If the above command returns the error to_string' is not a Member of Std, change -std=c++11 for -std=c++0x.

According to this article by IBM, the function std::to_string is a convenient way to implement what the function itoa makes. The same code, but for C++, can be made like this:

#include <iostream>
#include <string>

int main(){
    int numero;
    std::cout << "Digite um número: " << std::endl;
    std::cin >> numero;
    std::string str = std::to_string(numero);
    std::cout << "String " << str << std::endl;
}

---

If you use the Code::Blocks as IDE, and the message to_string' is not a Member of Std (or similar) appear to you, do the following:

• Click on Settings ➝ Compiler..

• Navigate to the tab Compiler Settings ➝ Compiler Flags

• Check the option Have g++ follow the Coming C++0x ISO language standard -Std=c++0x.

  

Compile and run the code again. This may not work in specific situations, but it usually solves.

---

Updating

Ultimately the problem was solved using the function sprintf, which can be used as follows:

#include <string>
#include <iostream>

#define LIMITE 10

int main(){
    int numero = 1234567890;
    char str[LIMITE];
    sprintf(str, "%d", numero);
    std::cout << str << std::endl;
}

Note: It is not always recommended to use sprintf, in this specific case it is known beforehand the size of the variable numero, then there are no major problems in using it, but in certain situations where it is not known the size that a variable can assume (be it reading a file or user input), to avoid leaks use the function snprintf.