Redefinition error with header files - cpp

Question

I have a template functions defined in a header file under a namespace. When I include this header in two source file in the same project. I don't get redefinition error.

/* template.h */
namespace x 
{
   template<typename T>
   function(t)
   {
       /* implementation */
   }
}

/*test.cpp*/
#include "template.h"

/* test2.cpp */
#inlcude "template.h"

In the above case I don't get any redefinition error. .Why I am not receiving any error?

That's because you don't define a *function* in your header file, you define a function *template*. I suggest you read e.g. [Why can templates only be implemented in the header file?](http://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file) for some more information. — Some programmer dude, Mar 09 '17 at 08:54
i dont understand - are you asking WHY you are NOT getting error? or what? Since header file included once in each cpp file, there is no redefinition - each cpp sees this header only once, so it is ok.... — Boris Bolshem, Mar 09 '17 at 08:55
What happens when I include template.h in multiple source files @Someprogrammerdude — dheeraj Vadlani, Mar 09 '17 at 09:03
it is ok to include header file to several source file. Each source file will get its own implementation — Boris Bolshem, Mar 09 '17 at 09:04

score 2 · Accepted Answer · answered Mar 09 '17 at 08:54

2

Because implicit template instantiations behave as if they were implicitly inline: all of them are consolidated into a single one at link-time.

answered Mar 09 '17 at 08:54

Quentin

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score 0 · Answer 2 · answered Mar 09 '17 at 09:12

0

Define the Header fine in the inner header file, when you include the inner header file to outer file all the headers will be included.

#ifndef FILE_H
#define FILE_H

/* ... Declarations etc here ... */

#endif

answered Mar 09 '17 at 09:12

Awais Rafique

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Redefinition error with header files - cpp

2 Answers2