cc -pipe -O   -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations math/M_PI_4l.c -o math/M_PI_4l -D_POSIX_C_SOURCE=202405L  -lm -lpthread -lrt  -lrt -lcrypt
math/M_PI_4l.c:8:26: error: 'M_PI_4l' undeclared here (not in a function); did you mean 'M_PI_4'?
 long double  const foo = M_PI_4l;
                          ^~~~~~~
                          M_PI_4