gcc -pthread -Wall -Wextra -Werror=implicit-function-declaration sys_mman/posix_typed_mem_open.c -o sys_mman/posix_typed_mem_open -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lxnet -lsocket -latomic sys_mman/posix_typed_mem_open.c: In function 'main': sys_mman/posix_typed_mem_open.c:18:9: error: implicit declaration of function 'posix_typed_mem_open' [-Wimplicit-function-declaration] 18 | posix_typed_mem_open("", 0, 0); | ^~~~~~~~~~~~~~~~~~~~