Question

I am trying to run a simple program in cygwin that includes fork and wait.
I thought it would be very easy to compile but I am having problems.

#include <stdio.h>  
#include <unistd.h>

void testFork(){}

int main(int argc,char* argv[]){

    if (fork()==0) {testFork();return 0;}
    while (wait() == -1);
    return 0;
}

Compiled using:
gcc -Wall -Wextra -o test.o test

I get the following error:

C:\Users\Aaron\AppData\Local\Temp\ccgh3MfS.o:ostest.c:(.text+0x11): undefined reference to `fork'
C:\Users\Aaron\AppData\Local\Temp\ccgh3MfS.o:ostest.c:(.text+0x22): undefined reference to `wait'
collect2: ld returned 1 exit status

I’m sure I’m missing something trivial. Any ideas?

Answer 1

The linker can’t find the standard C libraries.

Did you install Cygwin in the normal way? (Here’s a simple guide: http://www.eecg.utoronto.ca/~aamodt/ece242/cygwin.html).

Have you been able to compile even simpler programs:

#include <stdio.h>

int main(int argc, char **argv) {
    printf("Found C library.\n");
}

If that doesn’t compile, you might just want to try removing and reinstalling Cygwin – something is broken.