I have a question about the __syscall_return macro, in include/asm-i386/unistd.h : /* * user-visible error numbers are in the range -1 - -128: see * <asm-i386/errno.h> */ #define __syscall_return(type, res) \ do { \ if ((unsigned long)(res) >= (unsigned long)(-(128 + 1)) {\ errno = -(res); \ res = -1; \ } \ return (type) (res); \ } while (0) My question is: if the system call returned -129, errno will be set to 129, which, as the commment says, is not a legal value (i.e. the value 129 is not defined for errno in errno.h). Can someone please explain me why the test is >= -(128+1) instead of >= -128 ? Thank you.
