cc -O2 -pipe -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations complex/ctanl.c -o complex/ctanl -D_POSIX_C_SOURCE=202405L  -lm -lpthread -lrt  -lstdthreads -lcrypt
complex/ctanl.c:5:51: error: call to undeclared library function 'ctanl' with type '_Complex long double (_Complex long double)'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
    5 | long double complex (*foo)(long double complex) = ctanl;
      |                                                   ^
complex/ctanl.c:5:51: note: include the header <complex.h> or explicitly provide a declaration for 'ctanl'
1 error generated.