cc -O2 -pipe -pthread -Wall -Wextra -Werror=implicit-function-declaration time/getdate.c -o time/getdate -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lstdthreads -lcrypt time/getdate.c:44:18: error: call to undeclared function 'getdate'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration] 44 | struct tm* tm = getdate("2000-01-01 02:03:04"); | ^ time/getdate.c:44:13: error: incompatible integer to pointer conversion initializing 'struct tm *' with an expression of type 'int' [-Wint-conversion] 44 | struct tm* tm = getdate("2000-01-01 02:03:04"); | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ time/getdate.c:46:33: error: use of undeclared identifier 'getdate_err' 46 | errx(1, "getdate failed: %i", getdate_err); | ^ 3 errors generated.