Why do I get “undefined reference” errors even when I include the right header files?

Question

When I tried to compile this program, it failed:

#include 
#include 
#include 
#include 

voi         


        

Answer 1

Others have mentioned that you haven't linked with the pthread library using the -lpthread flag. Modern GCC (not sure how modern, mine is 4.3.3) allows you to use just -pthread. From the man page:

-pthread
Adds support for multithreading with the pthreads library. This option sets flags for both the preprocessor and linker.