Header file with function implementation problem

[bcpkh]

Hello All

Received a header file from a supplier that defines an interface to
implement but it's giving me a problem, I reproduce the general
structure of the header file below;

#ifndef XYZ_H

various #define(s)

#ifndef _ABC

void someFunc();

void someOtherFunc();

void implementedFunc() {
xyz;
}

#endif

#endif

The problem is that all my files that include this header xyz.h
complains about multiple definition of symbol implemetedFunc().

We are running HP-UX on Itanium.

Any advice would be appreciated.

Thank you,

B

 

[Keith Thompson]

Hello All

Received a header file from a supplier that defines an interface to
implement but it's giving me a problem, I reproduce the general
structure of the header file below;

#ifndef XYZ_H

various #define(s)

#ifndef _ABC

void someFunc();

void someOtherFunc();

void implementedFunc() {
xyz;
}

#endif

#endif

The problem is that all my files that include this header xyz.h
complains about multiple definition of symbol implemetedFunc().

We are running HP-UX on Itanium.

Any advice would be appreciated.

Function definitions don't belong in headers.

You said that the header "defines in interface to implement". Perhaps
the implementation of implementedFunc is just shown as an example. If
you're expected to modify the header for your own use anyway, it's not
much of a problem. If you're expected to use it as is, complain to
the supplier.

 

[viza]

Function definitions don't belong in headers.

What about static / inline / static inline functions?

 

[Stephen Sprunk]

Received a header file from a supplier that defines an interface to
implement but it's giving me a problem, I reproduce the general
structure of the header file below;

#ifndef XYZ_H

various #define(s)

Did you remember to #define XYZ_H here? Without that, your header guard
does nothing.

#ifndef _ABC
>
void someFunc();

void someOtherFunc();

void implementedFunc() {
xyz;
}

#endif

#endif

The problem is that all my files that include this header xyz.h
complains about multiple definition of symbol implemetedFunc().

Unless the function is static (and preferably inline too), the
definition should not be in a header, only a declaration. All normal
function definitions go in a .c file.

S

 

[Barry Schwarz]

Hello All

Received a header file from a supplier that defines an interface to
implement but it's giving me a problem, I reproduce the general
structure of the header file below;

#ifndef XYZ_H

various #define(s)

Can we assume one of these is for XYZ_H?

#ifndef _ABC

void someFunc();

You do realize that none of these are valid prototypes. Hopefully
*you* left out the parameter specifications for the sake of brevity
and they are included in the header.

void someOtherFunc();

void implementedFunc() {
xyz;
}

This is not a declaration but a definition. And still not a
prototype.

#endif

#endif

The problem is that all my files that include this header xyz.h
complains about multiple definition of symbol implemetedFunc().

The include guard (XYZ_H) only protects you from multiple inclusion in
the same translation unit (source file) and then only if there is a
#define directive for it in some of the code you omitted.

The multiple definition guard (_ABC) requires you to decide in which
source file (singular) you want the definition of implementedFunc to
appear. In all other source files, you need to include the
preprocessing directive
#define _ABC
so that the compiler will know to skip over the definition of
implementedFunc. Without this directive, implementedFunc will be
compiled with each source file that includes xyz.h and the linker will
correctly report that it is defined multiple times.

By the way, this approach sucks. At the very least the test should be
reversed so you only have to specify _ABC once instead on n-1 times.
But functions and objects should never be defined in a header file
anyway, only declared. The supplier should provide you either
1 - the object file for implementedFunc in a format suitable for
your linker, or
2 - the source file for implementedFunc separate from xyz.h so
you can compile it yourself.


Remove del for email

 

[EventHelix.com]

Hello All

Received a header file from a supplier that defines an interface to
implement but it's giving me a problem, I reproduce the general
structure of the header file below;

#ifndef XYZ_H

various #define(s)

#ifndef _ABC

void someFunc();

void someOtherFunc();

void implementedFunc() {
xyz;

}

#endif

#endif

The problem is that all my files that include this header xyz.h
complains about multiple definition of symbol implemetedFunc().

We are running HP-UX on Itanium.

Any advice would be appreciated.

Thank you,

B

The header file multiple inclusion is not implemented correctly.

The following article should help:

http://www.eventhelix.com/realtimemantra/HeaderFileIncludePatterns.htm

 

[Ian Collins]

What about static / inline / static inline functions?

They are OK, your example was neither.