clang -O2  -Wall -Wextra -Werror=implicit-function-declaration semaphore/sem_close.c -o semaphore/sem_close -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
../out/minix/basic/semaphore/sem_close.o: In function `main':
semaphore/sem_close.c:(.text+0x341): undefined reference to `sem_open'
semaphore/sem_close.c:(.text+0x39f): undefined reference to `sem_open'
semaphore/sem_close.c:(.text+0x3ad): undefined reference to `sem_close'
semaphore/sem_close.c:(.text+0x3c5): undefined reference to `sem_unlink'
clang: error: linker command failed with exit code 1 (use -v to see invocation)