cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations stdatomic/atomic_flag_clear.c -o stdatomic/atomic_flag_clear -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
ld: error: undefined symbol: atomic_flag_clear
>>> referenced by atomic_flag_clear.c
>>>               ../out/openbsd/include/stdatomic/atomic_flag_clear.o:(foo)
cc: error: linker command failed with exit code 1 (use -v to see invocation)