cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations math/M_2_SQRTPIl.c -o math/M_2_SQRTPIl -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
math/M_2_SQRTPIl.c:8:26: error: use of undeclared identifier 'M_2_SQRTPIl'
    8 | long double  const foo = M_2_SQRTPIl;
      |                          ^
1 error generated.