menu "C/C++ and POSIX layer" config RT_USING_EXTERNAL_LIBC bool help This is for external libc(e.g. mlib), and NOT for newlib or picolibc which are inherent in the toolchains. Usually, the external libc should be a software package and select RT_USING_EXTERNAL_LIBC in software package's Kconfig This option is not available for users to select. source "$RTT_DIR/components/libc/compilers/common/Kconfig" source "$RTT_DIR/components/libc/posix/Kconfig" source "$RTT_DIR/components/libc/cplusplus/Kconfig" endmenu