Messages in this thread | | | Date | Sun, 29 Oct 2006 06:00:25 -0500 (EST) | From | "Robert P. J. Day" <> | Subject | "signed" versus "__signed__" versus "__signed" in arch-specific "types.h" files |
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more annoying, nitpicky pedantry as i continue my tour of the kernel source. what is the rationale behind using the gcc keyword alias "__signed__" in many of the architecture-specific types.h files?
the general form of many of those files is:
=================== #ifndef __ASSEMBLY__
/* * __xx is ok: it doesn't pollute the POSIX namespace. Use these in the * header files exported to user space */
typedef __signed__ char __s8; <-- see? typedef unsigned char __u8;
typedef __signed__ short __s16; <-- here, too, and so on. typedef unsigned short __u16; ... #ifdef __KERNEL__ #ifndef __ASSEMBLY__
typedef signed char s8; <-- but now, things change typedef unsigned char u8;
typedef signed short s16; typedef unsigned short u16; ... ===================
so the keyword alias "__signed__" is used early on in nearly every types.h file but, if __KERNEL__ is defined, the file falls back to just using "signed". (the use of "unsigned" is, of course, consistent throughout.)
so, first, what is the rationale behind the use of "__signed__" in this context? and is there any reason that most of that content can't be centralized in a single arch-independent file and simply #include'd? for the most part, that general content looks identical regardless of the architecture. (in some cases, the files are *absolutely* identical, such as for arm and arm26, and one would think that a simple #ifdef or two could handle differing word sizes of the architecture.)
however, having said all that, there are some puzzling exceptions to the above pattern. asm-ia64/types.h typedefs the second set based on the *earlier* typedefs:
============================= ... typedef __signed__ int __s32; typedef unsigned int __u32;
typedef __signed__ long __s64; typedef unsigned long __u64;
/* * These aren't exported outside the kernel to avoid name space clashes */ # ifdef __KERNEL__
typedef __s8 s8; <-- like that typedef __u8 u8;
typedef __s16 s16; typedef __u16 u16; ... =============================
then there's asm-mips/sh/types.h, which *continues* to use "__signed__" after everyone else switches to merely "signed":
============================= ... #ifdef __KERNEL__
#define BITS_PER_LONG 32
#ifndef __ASSEMBLY__
typedef __signed__ char s8; <-- still using that gcc keyword alias typedef unsigned char u8;
typedef __signed__ short s16; typedef unsigned short u16; ... =============================
and, finally, there's include/asm-mips/types.h, which curiously introduces "__signed":
============================= ... #ifdef __KERNEL__
#define BITS_PER_LONG _MIPS_SZLONG
#ifndef __ASSEMBLY__
typedef __signed char s8; <-- ????? typedef unsigned char u8;
typedef __signed short s16; typedef unsigned short u16; ... =============================
is there any reason why a lot of this can't be standardized? it certainly looks like a lot of unnecessary duplication, interspersed with puzzling anomalies just to keep life interesting. :-)
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