Declaring a Structure in a Header File

[TheBattlizer]

I'm trying to declare a structure definition in a header file so I can use the structure in other files, however I get the error:
error C2011: 'Points' : 'struct' type redefinition
from the file where the structure definition is declared. The structure is only defined in that header file.

This is all of the code in the header file:

struct Points {
int xCoordinate; 
int yCoordinate; 
int zCoordinate;
}; // end of struct Points definition

The name of the header file is StructPoints.h and there is no accompanying C++ file.

Also, this header is used in other files source and header files. If I include the header in a file called Test.h, would I also need to include it in a file called Test.cpp?

And is there anything else I need to add to make this header work?

[Dave Sinkula]

http://en.wikipedia.org/wiki/Include_guard

[Ancient Dragon]

You might want to put code guards in that header file to prevent the problem you describe.

#ifndef POINTS_H
#define POINTS_H
struct Points {
int xCoordinate; 
int yCoordinate; 
int zCoordinate;
}; // end of struct Points definition
#endif

[ttqtrang146]

Dear TheBattlizer,
I think you could declare 2 structures with same name. If you include Test.h into file Test.cpp, you don't need to include StructPoints.h into file Test.cpp when it included into file Test.h

[ArkM]

Try to understand the standard compilation process logic.

Simplified translation process description:

1. Every .cpp file is processed separately (as if no other cpp files)

2. Preprocessor stage: process all # directives. Every active (see AD's post, #ifdef/#ifndef directives) #include directive in .cpp file is replaced by referred .h (or other) file or header (named in angle brackets) contents (recursively, until all includes are replaced)

3. This is a translation unit text. It's compiled.

Now consider your case. You have Points definition in structpoints.h file. You have #include "structpoints.h" in test.h file. You have #include "structpoints.h" and #include "test.h" directives in test.cpp. Now try to compile test.cpp - see points above:

1. Get test.cpp
2. Replace #include "structpoints.h" . It's Points definition. Replace #include "test.h" to its contents and recursively replace yet another #include "structpoints.h" ! That's yet another Points definition in this translation unit - you breaks "one definition" rule.

No magics...

Now try to understand AD's solution of the problem.