C / C++ / MFC

16-Mar-06 23:03

I have two C source files. One does not have main function, but it has a function called MyFunction(). I want to use this function into the other c file. How do I do it? I know i must create a header file (which defines MyFunction), and include it. I do not know how do I link it. (I am using TURBO C). It compiles, but when I try to make the .exe file, I get an error called Undefined symbo, _MyFunction. Please help me.

Regards

Aljechin Alexander Rose | [Rose]

RichardS16-Mar-06 23:24

16-Mar-06 23:24

Hi Aljechin,

Assuming file 1 is a.c and file 2 is b.c (with MyFunction() in b.c). Then you need to create a header file like b.h. Inside the b.h define a prototype of your function (e.g. void MyFunction (void);)

Then make sure that the b.h is included in each a.c and b.c. Then compilte both files.

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

<color>Aljechin 16-Mar-06 23:27

16-Mar-06 23:27

Halo Richard,

Before posting this i had done exactly the same. But there is a linker error:

Undefined symbol _MyFunction in a.c

can you please help me with a small example? it will take a minute for u but is trivially important for me now Frown | :(

Thanks
Aljechin

Sebastian Schneider16-Mar-06 23:32

Sebastian Schneider

16-Mar-06 23:32

File a.c:

<br />
#include "a.h"<br />
int myFunc(int a, int b)<br />
{<br />
   return a + b;<br />
}<br />
<br />
<br />

File a.h:

<br />
#ifndef _a_h_<br />
#define _a_h_<br />
<br />
int myFunc(int a, int b);<br />
<br />
#endif<br />
<br />
<br />

File b.c:

<br />
#include "a.h"<br />
<br />
int main( int argc, char* argv[] )<br />
{<br />
   int a = 15;<br />
   int b = 30;<br />
   int c = myFunc(a, b); // c = 45!<br />
   return 0;<br />
}

Cheers,
Sebastian

--
Contra vim mortem non est medicamen in hortem.

-- modified at 5:33 Friday 17th March, 2006

RichardS16-Mar-06 23:38

16-Mar-06 23:38

Hi Sebastian,

Just watch out, some C compilers don't like the // comments.

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

RichardS16-Mar-06 23:36

16-Mar-06 23:36

Hi,

First check that you are compiling both files. And if you are, make sure that you are compiling them in C mode.

a.c:

#include "b.h"
int main (int, char**)
{
   MyFunction ();
   return 0;
}

b.h:

#ifndef __B_H__
#define __B_H__
void MyFunction (void);
#endif /* __B_H__ */

b.c:

#include "b.h"
void MyFunction (void)
{
}

Hope this helps,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

<color>Aljechin 16-Mar-06 23:59

16-Mar-06 23:59

RichardS wrote:
First check that you are compiling both files. And if you are, make sure that you are compiling them in C mode.

How do i do this sir? Actually I am using Turbo C. I know i have to use the command line compiler (tcc.exe) for this, i do not know how to compile these files altogether. I want an object file of b.c and the functionality in that. Please help me.

Regards,
Aljechin

RichardS17-Mar-06 0:05

17-Mar-06 0:05

Unfortunately I used Turbo C very long time ago, just after Hannibal crossed the Alps. If you are using tcc.exe, I would then assume that the files are being compiled into C. The next thing to check is if you are getting object files a.o (or a.obj) and b.o (or b.obj). If you are not, you are not compiling both files. If you are, then check that you are linking all the objects together.

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

<color>Aljechin 17-Mar-06 0:08

17-Mar-06 0:08

RichardS wrote:
If you are, then check that you are linking all the objects together.

Sir, I have both the object files, a.obj and b.obj. How do I link them together? Please help me.

Regards,
Aljechin Alexander.

RichardS17-Mar-06 0:12

17-Mar-06 0:12

Umm, your first post said:

Aljechin It compiles, but when I try to make the .exe file, I get an error called Undefined symbo, _MyFunction.

How where you making a .exe?

By making a .exe file, you are linking the code.

regards,
Rich

p.s. It might help to see the command lines that you are using.

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

<color>Aljechin 17-Mar-06 0:19

17-Mar-06 0:19

Sir, I said I *tried* to make an exe file. I get this error when I tried to make the exe. Before making the exe itself the error comes from the linker. Frown | :(

Its actually for the exact command for which I am looking, i think. Can you please tell me that? I think its something like

tcc a.c, a.obj b.obj

Aljechin Alexander.

RichardS17-Mar-06 0:37

17-Mar-06 0:37

Ok. I think what you have done is slightly incorrect. With that command, tcc will create the a.obj and b.obj but the obj's will be identical (i.e. it will compile a.c into both a.obj and b.obj).

Try:

tcc a.c a.obj

for a.c and:

tcc b.c b.obj

for b.c.

Now to link there should be a TLINK.exe? Try:

tlink a.obj b.obj

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook