cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations math/M_PHIl.c -o math/M_PHIl -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
math/M_PHIl.c:8:26: error: use of undeclared identifier 'M_PHIl'
long double  const foo = M_PHIl;
                         ^
1 error generated.