I have many questions now. :) I think REG_L / REG_R / PTR_L / PTR_S macros are used by the size of the memory object size. Is this correct? For example, if I want to store a pointer (e.g. return address; which is 32-bit on N32) into a call frame RA slot (which is register_t == 64-bit on N32) on a stack, I should use REG_S, right? Masao