This error is often generated because you have typed the name of
a function or variable incorrectly. For example, the following code:
#include <stdio.h>
void print_hello()
{
printf ("Hello!\n");
}
/* To shorten example, not using argp */
int main()
{
Print_hello();
return 0;
}
generates the following rather forbidding error:
/tmp/cc9KXhmV.o: In function `main':
/tmp/cc9KXhmV.o(.text+0x1f): undefined reference to `Print_hello'
collect2: ld returned 1 exit status
The answer, however, is very simple. C is case-sensitive. The
main function calls the function Print_hello (with a
capital P), but the correct name of the function is
print_hello (with a lower-case p). The linker
could not find a function with the name Print_hello.
