When compiling with gcc cross compiler for OpenRISC 1000, many modules have NULL undefined. NULL is defined in stddef.h, but it is not included.
Please add #include stddef.h to modules that use NULL.
Are you talking about FreeRTOS kernel files? If so I’ve never seen that problem before and used many different compilers (20+). If it is the kernel files then you should be able to build by adding #define NULL ((void*)0) info FreeRTOSConfig.h.