cc -pthread -Wall -Wextra -Werror=implicit-function-declaration time/timer_create.c -o time/timer_create -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -liconv time/timer_create.c:16:2: error: unknown type name 'timer_t'; did you mean 'time_t'? 16 | timer_t timer; | ^~~~~~~ | time_t /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types/_time_t.h:31:33: note: 'time_t' declared here 31 | typedef __darwin_time_t time_t; | ^ time/timer_create.c:17:7: error: call to undeclared function 'timer_create'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] 17 | if ( timer_create(CLOCK_MONOTONIC, &event, &timer) < 0 ) | ^ 2 errors generated.