Does not include the strcat_s() function?

Question

My code is this:

#include <iostream>
#include <string>
#include <cstring>

using namespace std;
const int LENGTH1 = 25;

char array_str1[LENGTH1] = "Hey guys! "; 
char array_str2[] = "What's up?"; 

string std_str1 = "Hello everyone! ";
string std_str2 = "How's tricks?";

int main(){ 
    strcat_s(array_str1, LENGTH1, array_str2);
    std_str1 += std_str2;
    cout << std_str1 << endl;
    return 0;
}

When I run it, I get the error:

use of undeclared identifier 'strcat_s'

If I comment out the strcat_s line, the rest of the code runs fine.

I'm working from a tutorial, and even if I copy-paste the working code from the tutorial, I get the same error. I'm using Visual Studio Code 1.60.0 on MacOS 10.14.16.

[`strcat_s`](https://en.cppreference.com/w/c/string/byte/strcat) is a C function, it is not provided by C++. `` is a C++ header. — François Andrieux, May 10 '22 at 18:24
And why does C++ not provide such a useful-sounding function? Because it's not all that useful. Use `std::string`. — user4581301, May 10 '22 at 18:29
Visual Studio Code is not a compiler. Which compiler are you using with it? Some compilers provide `strcat_s`, some don't — Remy Lebeau, May 10 '22 at 18:32
My crystal ball tells me that "working code" from the tutorial is from an author utilizing the Visual C++ toolchain, which *does* include `strcat_s` (and all the other `insertnamehere_s` functions) as part of their implementation, including their C++ runtime. But it is *not* standard C++. MS even goes as far as providing a template version deducing the non-type template length parameter in the event you're using declared arrays (like you are); also utterly not part of the standard C++ library. — WhozCraig, May 10 '22 at 18:32
More specifically, `strcat_s` was introduced to the C language in C11. C++ does not promise to add functions that were added to another language. — Drew Dormann, May 10 '22 at 18:32
`#include ` -- A C++ looking at your code will quickly point out that you are including ``. So why are you using `strcat_s` and not `std::string`? — PaulMcKenzie, May 10 '22 at 18:32
*If I comment out the strcat_s line, the rest of the code runs fine.* -- And if you leave it commented out and instead used `std::string` throughout your code, you would be better off. — PaulMcKenzie, May 10 '22 at 18:34

eerorika · Answer 1 · 2022-05-10T18:43:24.000

2

Is <cstring> not including the strcat function?

<cstring> does declare std::strcat.

Sidenote: Don't use std::strcat; you won't need it. Use std::string.

strcat_s(array_str1, LENGTH1, array_str2);

strcat_s is not std::strcat. Even though there is std::strcat in the C++ standard library, there is no strcat_s.

Sidenote: There is strcat_s in the C standard library (since C11). C is a different language. Even in C, strcat_s is not guaranteed to be supported, and not all language implementations provide it.

edited May 10 '22 at 18:43

answered May 10 '22 at 18:28

eerorika

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All of which only goes to demonstrate, lest we forget, that C++ is no longer a 'superset' of C. – Paul Sanders May 10 '22 at 20:55
... So if you're going to code in C++, you should forget everything you know about C and [do it properly](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). – Paul Sanders May 10 '22 at 21:02

Does not include the strcat_s() function?

1 Answers1