Where should I include <string>?

Question

I am still getting used to working with C/C++ and I don't want to 'overinclude' libraries.

I have a header where I would like to place methods for reading input data as well as those variables which I call ofun.h because it handles information pertaining to the objective function I am trying to optimize. In this header, I need the name of the data defined as string data_name;.

Should I #include <string> inside this header file? If this happens and I include <string> in another header file, say file_io.h, and then in my main routine I call

#include <string>
#include "ofun.h"
#include "file_io.h"

will this cause problems? If so, what is the best way/place to include standard libraries like this so that they don't collide?

The #ifndef..#endif guards will take care of it. It is only a problem if you are compiling on a very slow device (eg floppy disk). — cup
– cup, Commented Jun 5, 2014 at 14:36

wolfPack88 · Accepted Answer · 2014-06-05 15:15:16Z

6

If anything within the header needs declarations included within <string>, I'd go ahead and include it within the header file. The best practice to ensure header files don't collide is to use include guards: http://en.wikipedia.org/wiki/Include_guard. Basically, you surround the declarations in your header with this:

#ifndef OFUN_H_
#define OFUN_H_

//your header here

#endif

This is, for example what you'd put in ofun.h. All of the standard library header files already have the include guard in them, you just need to make sure you put them in your own header files.

edited Jun 5, 2014 at 15:15

answered Jun 5, 2014 at 14:37

wolfPack88

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6 Comments

drjrm3 Over a year ago

Thanks, I'm using include guardes on __ofun__ but wasn't sure it was guarding against double includes of <string>

wolfPack88 Over a year ago

All standard C++ headers have the include guard in them, so you can even type in #include <string> three times in a row in the same file, and nothing bad will happen. Obviously, though, that won't actually accomplish anything, so stick with only including it once.

Mike Seymour Over a year ago

Please don't suggest using reserved names for include guards.

wolfPack88 Over a year ago

@MikeSeymour: I didn't do that, did I? I'm not sure what you mean.

Mike Seymour Over a year ago

@wolfPack88: Names like _OFUN_H_, beginning with an underscore followed by an upper-case letter, are reserved. See the question I linked to for details.

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Vandervidi · Accepted Answer · 2014-06-05 14:38:21Z

1

If you need this library in ofun.h for example, then include it in there. if you need it both in ofun.h and in the file including ofun.h , you can include it only in ofun.h.

answered Jun 5, 2014 at 14:38

Vandervidi

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Comments

ABu · Accepted Answer · 2014-06-05 14:53:18Z

1

Don't be afraid. For consistence sake, put every header you need in every file which uses identifiers declared in such header, even if a chain of includes repeats headers.

Guards will be care of you about that.

answered Jun 5, 2014 at 14:53

ABu

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