Question

In my main() method in one source file, I have a call to pthread_create(), as follows:

pthread_t pth_chanrecv;
pthread_create(&pth_chanrecv, NULL, chanrecv_run, NULL);

“chanrecv_run” is a function in another source file that I have written.
This is the function prototype:

void *chanrecv_run(void *arg);

The function prototype is in a header file which I have included in the source file containing the main() method.

I’m compiling my program with the following statement:

gcc -lpthread -o bin/main2 src/main2.c

The chanrecv_run() function is in a file named “chanrecv.c”, also in the src folder.

Every time I try and compile it, I get the following error:

/tmp/ccHxRSTk.o: In function `main':
main2.c:(.text+0x256): undefined reference to `chanrecv_run'
collect2: ld returned 1 exit status

I have no idea what’s going wrong. I’ve scoured the web trying to find another instance of someone trying to call a function that was in another file with the pthread_create function and come up completely blank. Is this even possible, and if so, how?

Answer 1

The issue isn’t pthreads related. Since you’ve not linked your second .c file containing the chanrecv_run function the linker is moaning.

You need:

gcc -lpthread -o bin/main2 src/main2.c src/file_with_chanrecv_run_in.c