cc -O2 -pipe -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations math/M_EGAMMA.c -o math/M_EGAMMA -D_POSIX_C_SOURCE=202405L  -lm -lpthread -lrt  -lstdthreads -lcrypt
math/M_EGAMMA.c:8:21: error: use of undeclared identifier 'M_EGAMMA'
    8 | double  const foo = M_EGAMMA;
      |                     ^
1 error generated.