Question

So I made a program that uses four differrent processes to do some stuff. I works perfectly, but now I want to split it up so each of the processes has its own .c file. I tried to do this using a header file “processes.h” that has the function prototypes for all the processes. It looks like this:

#ifndef PROCESSES_H_
#define PROCESSES_H_

/*------------------------------------------------------------------------------
                definitions (defines, typedefs, ...)
------------------------------------------------------------------------------*/
#define NR_OF_PROCESSES 4

enum errCode {
    ERR_NONE = 0, ERR_SYNTAX, ERR_OPEN, ERR_TOKEN, ERR_ARG, ERR_END
};
typedef enum errCode ErrCode;

enum toktype {
    NUMBER = 0, OPERATOR, ENDOFLINE, ENDOFFILE
};
typedef enum toktype Token;


/*------------------------------------------------------------------------------
                function prototypes               
------------------------------------------------------------------------------*/
void readProcess(int pfds[5][2]);
void tokenProcess(int pfds[5][2]);
void calculatorProcess(int pfds[5][2]);
void errorProcess(int pfds[5][2]);

/*------------------------------------------------------------------------------
                global variable declarations                   
------------------------------------------------------------------------------*/
void (*functionTable[NR_OF_PROCESSES]) (int pfds[5][2]) = {
    readProcess,
    tokenProcess,
    calculatorProcess,
    errorProcess
};


#endif /*PROCESSES_H_*/

All the .c files which contain the implementation of the function #include “processes.h”, and the main function (which uses the functionTable to set up the processes) also includes processes.h.

When I try to compile I get the error:

ld: duplicate symbol _functionTable in /var/folders/eH/eHF8LmdvHzSsNgT01V3jyk+++TI/-Tmp-//ccDgTW2X.o and /var/folders/eH/eHF8LmdvHzSsNgT01V3jyk+++TI/-Tmp-//ccp7zO9L.o
collect2: ld returned 1 exit status

Is this the right way of doing the splitting up into different files? Or do I need a separate .h file for each .c file?

Answer 1

Put this in your .h:

extern void *functionTable;

Then put this in exactly one file, e.g. the source file with “main()”:

#include "processes.h"
...
void (*functionTable[NR_OF_PROCESSES]) (int pfds[5][2]) = {
    readProcess,
    tokenProcess,
    calculatorProcess,
    errorProcess
};