clang -O2 -Wall -Wextra -Werror=implicit-function-declaration semaphore/sem_destroy.c -o semaphore/sem_destroy -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lintl ../out/minix/basic/semaphore/sem_destroy.o: In function `main': semaphore/sem_destroy.c:(.text+0x30e): undefined reference to `sem_init' semaphore/sem_destroy.c:(.text+0x31a): undefined reference to `sem_destroy' clang: error: linker command failed with exit code 1 (use -v to see invocation)