Undefined reference error [duplicate] - c

Question

This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 6 years ago.
EDIT: A complete duplicate of course, isn't the whole point of stackoverflow to ask questions, and get specific answers, the 'answer' you linked me to is:
A. For C++, so partly unintelligible
B. Reads like a wiki article, it is massive, and not specific in the slightest, or in the least bit helpful.
I have copied an example bit of code from the examples folder in the code library (libftdi) I downloaded, to where I want to write my project, when I run it, it has a lot of undefined references, however it runs fine in its original location.
Main file:
#include <stdio.h>
#include <stdlib.h>
#include <ftdi.h>
int main(void)
{
int ret, i;
struct ftdi_context *ftdi;
struct ftdi_device_list *devlist, *curdev;
char manufacturer[128], description[128];
int retval = EXIT_SUCCESS;
if ((ftdi = ftdi_new()) == 0)
{
fprintf(stderr, "ftdi_new failed\n");
return EXIT_FAILURE;
}
if ((ret = ftdi_usb_find_all(ftdi, &devlist, 0, 0)) < 0)
{
fprintf(stderr, "ftdi_usb_find_all failed: %d (%s)\n", ret, ftdi_get_error_string(ftdi));
retval = EXIT_FAILURE;
goto do_deinit;
}
printf("Number of FTDI devices found: %d\n", ret);
i = 0;
for (curdev = devlist; curdev != NULL; i++)
{
printf("Checking device: %d\n", i);
if ((ret = ftdi_usb_get_strings(ftdi, curdev->dev, manufacturer, 128, description, 128, NULL, 0)) < 0)
{
fprintf(stderr, "ftdi_usb_get_strings failed: %d (%s)\n", ret, ftdi_get_error_string(ftdi));
retval = EXIT_FAILURE;
goto done;
}
printf("Manufacturer: %s, Description: %s\n\n", manufacturer, description);
curdev = curdev->next;
}
done:
ftdi_list_free(&devlist);
do_deinit:
ftdi_free(ftdi);
return retval;
}
Error:
ollieb#ursus ~/Documents/BitBang $ make
make bitbang
make[1]: Entering directory '/home/ollieb/Documents/BitBang'
cc -Wall -g -I/usr/include/libftdi1/ bitbang.c -o bitbang
/tmp/cc20kltT.o: In function `main':
/home/ollieb/Documents/BitBang/bitbang.c:13: undefined reference to `ftdi_new'
/home/ollieb/Documents/BitBang/bitbang.c:19: undefined reference to `ftdi_usb_find_all'
/home/ollieb/Documents/BitBang/bitbang.c:21: undefined reference to `ftdi_get_error_string'
/home/ollieb/Documents/BitBang/bitbang.c:32: undefined reference to `ftdi_usb_get_strings'
/home/ollieb/Documents/BitBang/bitbang.c:34: undefined reference to `ftdi_get_error_string'
/home/ollieb/Documents/BitBang/bitbang.c:42: undefined reference to `ftdi_list_free'
/home/ollieb/Documents/BitBang/bitbang.c:44: undefined reference to `ftdi_free'
collect2: error: ld returned 1 exit status
<builtin>: recipe for target 'bitbang' failed
make[1]: *** [bitbang] Error 1
make[1]: Leaving directory '/home/ollieb/Documents/BitBang'
Makefile:4: recipe for target 'all' failed
make: *** [all] Error 2
Make file:
CFLAGS=-Wall -g -I/usr/include/libftdi1/
all:
make bitbang
clean:
rm bitbang

Answer 1

You have to link against the ftdi library (-Llibdirectory -llib)