Definition in Header files

[Madhur]

I have problems faced in adding definitions in the command header
file. I have defined a header file which includes huge set of global
constants and I am using them in all the C files.

For example my sample.h file looks like this

/*************

File : sample.h

****************/
const int a1 = 0;
const int a2 = 0;
/****End of sample.h*********/
My source code looks like this

/*****************
File:sample1.c

***********/
#include "sample.h"

int main()
{
}

/*****End of sample1.c************/

/***************
File : sample2.c
**************/

#include "sample.h

int main()
{
}

/*******End of sample2.c**********/

Now the problem is during linking it says multiple definition of
symbols a1 and a2. I can avoid this problem by having a C file which
contains the definitions and H file for declarations. But is there any
way I can avoid doing this. Please let me know.

[tragomaskhalos]

On Oct 23, 6:39 am, Madhur <[e-mail]:

I have problems faced in adding definitions in the command header
file. I have defined a header file which includes huge set of global
constants and I am using them in all the C files.

For example my sample.h file looks like this

/*************

File : sample.h

****************/

const int a1 = 0;
const int a2 = 0;

/****End of sample.h*********/

My source code looks like this

/*****************
File:sample1.c

***********/
#include "sample.h"

int main()
{

}

/*****End of sample1.c************/

/***************
File : sample2.c
**************/

#include "sample.h

int main()
{

}

/*******End of sample2.c**********/

Now the problem is during linking it says multiple definition of
symbols a1 and a2. I can avoid this problem by having a C file which
contains the definitions and H file for declarations. But is there any
way I can avoid doing this. Please let me know.

I think your problem is that, based on the extension,
these are C rather than C++ files.
In C++ a1 and a2 have internal linkage so you should have
no problem, but the rules in C, IIRC, are different.
So, rename the files to cpp or otherwise compile them as
C++. If they must remain C, put "static" in front of
the variable definitions.

[Howard]

"tragomaskhalos" <da*************@logicacmg.comwrote in message
news:11**********************@q3g2000prf.googlegro ups.com...

On Oct 23, 6:39 am, Madhur <[e-mail]:

>I have problems faced in adding definitions in the command header
file. I have defined a header file which includes huge set of global
constants and I am using them in all the C files.

For example my sample.h file looks like this

/*************

File : sample.h

****************/

const int a1 = 0;
const int a2 = 0;

/****End of sample.h*********/

My source code looks like this

/*****************
File:sample1.c

***********/
#include "sample.h"

int main()
{

}

/*****End of sample1.c************/

/***************
File : sample2.c
**************/

#include "sample.h

int main()
{

}

/*******End of sample2.c**********/

Now the problem is during linking it says multiple definition of
symbols a1 and a2. I can avoid this problem by having a C file which
contains the definitions and H file for declarations. But is there any
way I can avoid doing this. Please let me know.

I think your problem is that, based on the extension,
these are C rather than C++ files.
In C++ a1 and a2 have internal linkage so you should have
no problem, but the rules in C, IIRC, are different.
So, rename the files to cpp or otherwise compile them as
C++. If they must remain C, put "static" in front of
the variable definitions.

I'm pretty sure that's not the problem. The link error is probably because
there are no include guards in the header file, and the header file is
included by two files in the same compilation unit.

But you are correct that those should be .cpp files if he's using C++. The
main reason for that is because certain IDEs will use the C compiler instead
of the C++ compiler for files with a .c extension.

-Howard

[Victor Bazarov]

Howard wrote:

"tragomaskhalos" <da*************@logicacmg.comwrote in message
news:11**********************@q3g2000prf.googlegro ups.com...

>On Oct 23, 6:39 am, Madhur <[e-mail]:

>>I have problems faced in adding definitions in the command header
file. I have defined a header file which includes huge set of global
constants and I am using them in all the C files.

For example my sample.h file looks like this

/*************

File : sample.h

****************/

const int a1 = 0;
const int a2 = 0;

/****End of sample.h*********/

My source code looks like this

/*****************
File:sample1.c

***********/
#include "sample.h"

int main()
{

}

/*****End of sample1.c************/

/***************
File : sample2.c
**************/

#include "sample.h

int main()
{

}

/*******End of sample2.c**********/

Now the problem is during linking it says multiple definition of
symbols a1 and a2. I can avoid this problem by having a C file which
contains the definitions and H file for declarations. But is there
any way I can avoid doing this. Please let me know.

I think your problem is that, based on the extension,
these are C rather than C++ files.
In C++ a1 and a2 have internal linkage so you should have
no problem, but the rules in C, IIRC, are different.
So, rename the files to cpp or otherwise compile them as
C++. If they must remain C, put "static" in front of
the variable definitions.

I'm pretty sure that's not the problem. The link error is probably
because there are no include guards in the header file, and the
header file is included by two files in the same compilation unit.

What *same compilation unit*? Separate .c files should mean separate
compilation, no?

But you are correct that those should be .cpp files [..]

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[James Kanze]

On Oct 23, 6:05 pm, "Howard" <[e-mail]:

"tragomaskhalos" <[e-mail] in message

[...]

I think your problem is that, based on the extension,
these are C rather than C++ files.
In C++ a1 and a2 have internal linkage so you should have
no problem, but the rules in C, IIRC, are different.
So, rename the files to cpp or otherwise compile them as
C++. If they must remain C, put "static" in front of
the variable definitions.

I'm pretty sure that's not the problem.

I'm almost 100% sure that it is the problem. Most of the C++
compilers I know will compile a file with the extension .c as C.
And in C, const doesn't mean internal linkage.

The link error is probably because
there are no include guards in the header file, and the header file is
included by two files in the same compilation unit.

That would cause a compile error, not a link error.

But you are correct that those should be .cpp files if he's
using C++. The main reason for that is because certain IDEs
will use the C compiler instead of the C++ compiler for files
with a .c extension.

Not the IDE's. Most "compilers" are actually driver programs,
which invoke different compilers, the linker, perhaps the
librarian, etc., depending on the options given and the filename
extensions. While g++ and Sun CC will compile .c as C++, VC++
(command cl) doesn't, and historically, I believe that many
others didn't either. (The fact that g++ and Sun CC don't
actually surprised me. I would, in fact, consider this a bug:
if I want to compile and link an application with both C and
C++, I want the C compiled as C, but I still need to invoke C++
for the link to work correctly.)

--
James Kanze (GABI Software) email:ja*********@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]