The source fortification is a security mitigation that replaces certain function calls with more secure wrappers that perform additional runtime or compile-time checks. Since a preprocessor macro determines source fortification, a typo in the macro spelling effectively disables it, and neither the libc nor the compiler catches this issue, unlike typos made in other security hardening options enabled with compiler flags instead of macros. Although compilers detect such a typo, the flag was used in a CMake script to determine if the compiler supports the safe stack mitigation.