Hello Ekaitz,
the issue here is that the CROSS_CPLUS_INCLUDE_PATH contains the C include path first, but cstdlib is using #include_next "stdlib.h". Since stdlib.h is previous to cstdlib in include paths, stdlib.h is not found as "next". As a workaround, change the order in this variable. Another issue you might have is the libstdc++ not being linked properly, that might be because currently it outputs to /lib inside of package output instead of arm-none-eabi/lib. You might try adding the $GUIX_ENVIRONMENT/lib into your CROSS_LIBRARY_PATH as a workaround. Regards, Rutherther
