facing problem with multiple source file porgram.

Hi ,
This is first time,i am trying to execute a program with multiple source files.
I have A.C ,B.C & a header file "header.h"(all attached here).A.C is supposed to use a function named "disp()" which is defined in B.C.
I declared the function "disp()" in the "header.h" and included the header in both A.C and B.C. But it is showing an error message as follows:
"Linker error: Undefined symbol _disp in module A.c"
I am using Turbo C++ 3.0 version.please help.Thank you for the help..

Well the first thing you need is a decent compiler for the modern age (and compatible with your operating system).

Unlike darth vader, this sad devotion to the ancient ways does NOT confer such users with special magical powers.

Pick one of these, all are used by the regulars, so there is no shortage of help.
Microsoft Express Downloads - Visual Studio Express and SQL Server Express
smorgasbordet - Pelles C
Code::Blocks

Oh, and you need to make sure ALL your .c files are added to the project, not just the one containing main().

Thank u for the response.I will certainly use any one of the modern compilers suggested by you.
But just for the sake of my curiosity,please tell "what is wrong with the code??".

Do you have both source files listed in the project?

Look at this example

Compile one source file only, get unresolved symbol
$ gcc a.c
/tmp/ccgoIGQn.o: In function `main':
a.c:(.text+0x7): undefined reference to `disp'
collect2: ld returned 1 exit status

Compile both, job is done.
$ gcc a.c b.c
b.c: In function ‘disp’:
b.c:5: warning: incompatible implicit declaration of built-in function ‘printf’

1) you are redeclaring disp() in your b.c file... the declaration in the header is enough.
2) you need to #include <stdio.h> in b.c as well as a.c

3) A and B are realy lousy file names for even a project this trivial.
4) void disp() is an invalid function definition that will work only in that crappy TurboC compiler...s/b... void disp(void)
5) It's int main (void) and it returns an errorlevel value at the end (usually 0).

There were few things which I has to change, before i got this running on my machine. But most of the issue have noted down but other in the previous post. But the other thing which i wanted specify is that C is a very typed language, even an alphabet can make a difference. In your A.c file you include the header file like

Code:

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#include "header.h"

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But there isn't file such that. You have HEADER..h. Should be renamed to 'header.h'

See my compiling process.

Code:

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Cygwin@Cygwin-PC ~/Code
$ gcc A.c B.c
A.c:7:2: warning: no newline at end of file

Cygwin@Cygwin-PC ~/Code
$ gcc -o output A.o B.o

Cygwin@Cygwin-PC ~/Code
$ ./output.exe
the disp function should work

Cygwin@Cygwin-PC ~/Code

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ssharish

Quote:

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Originally Posted by CommonTater

1) you are redeclaring disp() in your b.c file... the declaration in the header is enough.
2) you need to #include <stdio.h> in b.c as well as a.c

3) A and B are realy lousy file names for even a project this trivial.
4) void disp() is an invalid function definition that will work only in that crappy TurboC compiler...s/b... void disp(void)
5) It's int main (void) and it returns an errorlevel value at the end (usually 0).

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Thanks for the corrections mate.But even after the corrections,compiling the A.c is giving the same error:
"Linker error: Undefined symbol _disp in module A.c"
i am using a turbo C compiler.Shuld i use "extern" to declare "void disp(void)" function?

Quote:

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Originally Posted by learning"c"

Thanks for the corrections mate.But even after the corrections,compiling the A.c is giving the same error:
"Linker error: Undefined symbol _disp in module A.c"
i am using a turbo C compiler.Shuld i use "extern" to declare "void disp(void)" function?

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How to fix this...

1) uninstall Turbo C... and flush the disks down the toilet.

2) Go HERE and download the version (32 or 64 bit) relevent to your operating system.

3) Install

4) Read the help file... no joke... really read it!

5) Start your first project.

6) Rewrite the files using C-99 syntax as I explained.

7) Build...

8) Run.

It's not just your code that's the problem... it's your freaking Fred Flintstone compiler!

Quote:

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Originally Posted by CommonTater

4) void disp() is an invalid function definition that will work only in that crappy TurboC compiler...s/b... void disp(void)

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It is fine as part of a function definition and will work with any standard conforming C compiler. Actually, it is also fine as part of a function declaration that is not a function definition, but then writing it as void disp(void); would then make it certain that disp does not have any parameters.

Quote:

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Originally Posted by learning"c"

Thanks for the corrections mate.But even after the corrections,compiling the A.c is giving the same error:
"Linker error: Undefined symbol _disp in module A.c"
i am using a turbo C compiler.Shuld i use "extern" to declare "void disp(void)" function?

---

What exactly were the corrections that you made in the end? One of things to note is that you have a linker error: if you only compiled A.c, then that's where your problem lies. You should compile both source files and link them.

Quote:

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Originally Posted by laserlight

It is fine as part of a function definition and will work with any standard conforming C compiler. Actually, it is also fine as part of a function declaration that is not a function definition, but then writing it as void disp(void); would then make it certain that disp does not have any parameters.


What exactly were the corrections that you made in the end? One of things to note is that you have a linker error: if you only compiled A.c, then that's where your problem lies. You should compile both source files and link them.

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now files A.c ,B.c and header.h look like :
A.c

Code:

---

#include<stdio.h>
#include "header.h"
int main(void)
{
        disp();
        return 0;
}

---

B.c :

Code:

---

#include "header.h"
#include<stdio.h>
void disp(void)
{
        printf("the disp function should work");
}

---

header.h :

Code:

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#ifndef header_h_
#define header_h_
void disp(void);
#endif

---

thank you for the help :)

That's looks fine, though I would have written header_h_ as HEADER_H_. So, look into the linker error by compiling both source files and linking them.