clang -O2  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations math/M_EGAMMA.c -o math/M_EGAMMA -D_POSIX_C_SOURCE=202405L  -lm  -lintl
math/M_EGAMMA.c:8:21: error: use of undeclared identifier 'M_EGAMMA'
double  const foo = M_EGAMMA;
                    ^
1 error generated.