undefined reference to function in gcc pthreads C

Question

I have a code with pthreads named par.c , but when I try to compile it with the command: gcc par.c -lpthread -o par , it gives me this :

/tmp/ccAzMTL8.o: In function `compare': par.c:(.text+0x414): undefined reference to `exchange'

the function is

inline void exchange(int i, int j) {
  int t;
  t = a[i];
  a[i] = a[j];
  a[j] = t;
}

inline void compare(int i, int j, int dir) {
  if (dir==(a[i]>a[j])) 
    exchange(i,j);
}

And in main I have them both:

void compare(int i, int j, int dir);
inline void exchange(int i, int j);

Does anyone have any ideas why is this happening?

Answer 1

I'm assuming all the code you posted is in the same .c file.

I had the same problem in the past. You have to declare the implementations of the inline functions as static inline . static means the function can only be linked in the same compilation unit (like it's private to this .c file). This should be the case for inline function anyway, so I can't tell you why it makes a difference, but it worked for me.