Error(s):

/tmp/ccQK5eXT.o: In function `main':
source.c:(.text.startup+0x65): undefined reference to `pthread_create'
source.c:(.text.startup+0x74): undefined reference to `pthread_create'
source.c:(.text.startup+0x83): undefined reference to `pthread_create'
source.c:(.text.startup+0x94): undefined reference to `pthread_create'
source.c:(.text.startup+0xa0): undefined reference to `pthread_join'
source.c:(.text.startup+0xac): undefined reference to `pthread_join'
source.c:(.text.startup+0xb8): undefined reference to `pthread_join'
source.c:(.text.startup+0xc4): undefined reference to `pthread_join'
collect2: error: ld returned 1 exit status