Thread: Extern functions calls

Hi everyone, i'm using dev c++ 4.9.9.2. I have an application wich is compose by four files:

main.c
TIFFheader.c
TIFFheader.h
decs.h

In main.c file, i want to call some functions wich are located in TIFFheader.c. Also i've defined a user data type in TIFFheader.h that i want to use from main.c archive. For doing it, i include TIFFheader.h in main.c. In TIFFheader.c, i need to include TIFFheader.h too, because in this file i declare some useful constants, structures and all functions wich belong to TIFFheader.c. When i do that, i keep getting the error constants and structures were defined twice. So, how can i do to call functions, use structures and constants, from main.c and do it from TIFFheader.c too, without this error?
Regards!.

Sounds like you need include guards.

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

gg

Wow that was quick, thaks guys for your responses. I try codeplug's solution, but it just don't work. Here is what i'm trying to do, and also necessary file's code structure to help you understand me in a better manner.

TIFFheader.h

Code:

#ifndef  hfile_TIFFheader
#define hfile_TIFFheader

typedef struct s_tiff_header
{
    short lsb;
    long bitsPerPixel;
    long imageWidth;
    long imageHeight;
    long stripOffset;
}tiff_header;

... // constant declarations come here

... // declarations of  functions located at TIFFheader.c file

#endif

Decs.h

Code:

#include <stdlib.h>
#include <stdio.h>
#include <io.h>
#include <fcntl.h>
#include <dos.h>
#include <math.h>
#include <malloc.h>
#include <string.h>
#include <sys\types.h>
#include <sys\stat.h>
#include "TIFFheader.h"

... // unions declared here

TIFFheader.c

Code:

#include "decs.h"             // relevant line           

tiff_header getTiffHeader ( const char* filename )
{
    tiff_header header;
    char buffer[12];
    FILE *image;
    
    short notFinished,
          tag,
          tagValueType,
          directoriesCount;
    
    int i, 
        bytesRead;

    ... // function goes on, and others too

main.c

Code:

#include <stdio.h>
#include <stdlib.h>
#include "decs.h"           //relevant include

int main(int argc, char *argv[])
{
  tiff_header hdr;
  char filepath[20];
  
  printf ( "Ingrese la ruta de la imagen: \n" );
  scanf ( "%s" , filepath );
  printf ( "Usted ingreso %s", filepath );
  hdr = getTiffHeader ( filepath ); 
  system("PAUSE");	
  return 0;
}

The specific error is
multiple definition of __BYTE
multiple definition of __ASCII
multiple definition of __SHORT
multiple definition of __LONG
multiple definition of __RATIONAL
...

and so on with all constants declared below. So, it tells to me that i'm defined constant, but not functions and structures twice.
Am i applying codeplug's solution well?. I hope you can help me out on this guys.
Thanks in advance.

Are the constants extern'ed in the header files?

And are those your constants in the warnings?

No and yes, are the responses to your questions. Here is the declaration of the constants

Code:

/**********************************
* Tipo del valor del tag
***********************************/

const short __BYTE = 1;
const short __ASCII = 2;
const short __SHORT = 3;
const short __LONG = 4;
const short __RATIONAL = 5;

/**********************************
* Comienzo estructuras de 
* información dentro del tag
**********************************/

const int __TAGVALUEOFFSET = 8;
const int __TAGVALUETYPEOFFSET = 2;
const int __TAGVALUETYPELENGHTOFFSET = 4;
const int __TAGCLASSOFFSET = 0;

I did what matsp said. If i don't assigned a value to the constant at moment i declare it, errors dissapear, but when i try to give a value to the constant in one of the .c files (TIFFheader.c exactly speaking) errors appear again. So, now the trouble is how to assign the value to constant. I really appreciate how you are helping me, thanks guys.

That looks correct. What are the errors you're getting now?

gg

The error was the same, but i renamed consts, and it worked well!. Thank you all for helping me out. I'm really, really greateful.
Regards.