gcc -pthread  -Wall -Wextra -Werror=implicit-function-declaration unistd/confstr.c -o unistd/confstr -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lxnet -lsocket -latomic
unistd/confstr.c: In function 'main':
unistd/confstr.c:10:25: error: implicit declaration of function 'confstr' [-Wimplicit-function-declaration]
   10 |         size_t needed = confstr(_CS_PATH, NULL, 0);
      |                         ^~~~~~~