RSIZE_MAX is defined in stdint.h, but protected from compilation by "#if __POCC_TARGET__ == 3".
However, this feature is C11 related, not connected to a target. When compiling for X86, __POCC_TARGET__ is 1, not 3 (AMD64). Should this not have been guarded by #if __STDC_VERSION__ == 201112L" or something like that that?