CODEWITHSUNDEEP
cgccmakefile
logitech mouse
logitech mouse

Reputation: 91

`multiple definition of` lots of variables error - is my make file incorrect?

I am getting an error when I compile multiple definition of lots of variables. For example:

/tmp/ccwHwJ7t.o:(.data+0x0): multiple definition of `serial_number'
/tmp/ccmT1XNI.o:(.data+0x0): first defined here

All the variables are located in ftdi.h, which is included by main.c. Is there something wrong with my make file that is causing this to be included twice? or am I looking in the wrong directio.

SSHELL = /bin/sh
CC    = gcc

APP = npi_usb_ftdi
INC = include

INCDIRS +=-I${INC}

CFLAGS= ${INCDIRS} -Wall -Wextra
LIBS = libftd2xx.a  -ldl -lpthread -lrt


all: ${APP}

${APP}: src/main.c src/ftdi.c src/vt100.c src/monitor.c
    ${CC} ${CFLAGS} src/main.c src/ftdi.c src/vt100.c src/monitor.c -o ${APP} ${LIBS} 

ftdi.o:
    ${CC} -c -o src/ftdi.o src/ftdi.c

vt100.o:
    ${CC} -c -o src/vt100.o src/vt100.c

monitor.o:
    ${CC} -c -o src/monitor.o src/monitor.c


clean:
    rm -f src/*.o ; rm -f src/*~ ; rm -f *~ ; rm -f ${APP}

Upvotes: 1

Views: 722

Answers (1)

Paul Ogilvie
Paul Ogilvie

Reputation: 25286

You probably include the .h file in other source files too. No problem, but only in one source file should the variables be declared and in the others just defined. I use:

// ftdi.h
#ifndef EXTERN
# define EXTERN extern
#endif
EXTERN int examplevar;

// main.c
#define EXTERN
#include "ftdi.h"

// ftdi.c
#include "ftdi.h"

Upvotes: 1

Related Questions