Re: [PATCH] const vs. __attribute__((const)) confusion

From: Nikita Danilov
Date: Tue Jan 20 2004 - 05:29:15 EST

Linux Kernel Mailing List writes:
> ChangeSet 1.1490.3.216, 2004/01/19 10:43:54-08:00, akpm@xxxxxxxx
>
> [PATCH] const vs. __attribute__((const)) confusion
>
> From: "H. Peter Anvin" <hpa@xxxxxxxxx>
>
> Declaring a function to return a const scalar value is pretty meaningless.
> These functions are really trying to say that they don't alter any external
> state.
>
> Fix that up by using __attribute__((const)), if the compiler supports that.
>

Let's then also replace all existing usages of __attribute__((const))
with __attribute_const__, while we are here.

I don't have the hardware to test this patch, but at least it compiles.

Nikita.
===== arch/ia64/kernel/unwind.c 1.35 vs edited =====
--- 1.35/arch/ia64/kernel/unwind.c Mon Jan 5 18:47:54 2004
+++ edited/arch/ia64/kernel/unwind.c Tue Jan 20 13:13:07 2004
@@ -650,7 +650,7 @@

/* Unwind decoder routines */

-static enum unw_register_index __attribute__((const))
+static enum unw_register_index __attribute_const__
decode_abreg (unsigned char abreg, int memory)
{
switch (abreg) {
===== drivers/usb/class/audio.c 1.42 vs edited =====
--- 1.42/drivers/usb/class/audio.c Thu Oct 23 16:59:04 2003
+++ edited/drivers/usb/class/audio.c Tue Jan 20 13:13:39 2004
@@ -203,12 +203,12 @@

#define AUDIO_DEBUG 1

-#define SND_DEV_DSP16 5
+#define SND_DEV_DSP16 5

#define dprintk(x)

#undef abs
-extern int abs(int __x) __attribute__ ((__const__)); /* Shut up warning */
+extern int abs(int __x) __attribute_const__; /* Shut up warning */

/* --------------------------------------------------------------------- */

===== include/asm-alpha/byteorder.h 1.2 vs edited =====
--- 1.2/include/asm-alpha/byteorder.h Wed Feb 19 22:30:42 2003
+++ edited/include/asm-alpha/byteorder.h Tue Jan 20 13:23:50 2004
@@ -6,7 +6,7 @@

#ifdef __GNUC__

-static __inline __u32 __attribute__((__const)) __arch__swab32(__u32 x)
+static __inline __u32 __attribute_const__ __arch__swab32(__u32 x)
{
/*
* Unfortunately, we can't use the 6 instruction sequence
===== include/asm-arm/current.h 1.3 vs edited =====
--- 1.3/include/asm-arm/current.h Sat Dec 28 19:26:45 2002
+++ edited/include/asm-arm/current.h Tue Jan 20 13:23:50 2004
@@ -3,7 +3,7 @@

#include <linux/thread_info.h>

-static inline struct task_struct *get_current(void) __attribute__ (( __const__ ));
+static inline struct task_struct *get_current(void) __attribute_const__;

static inline struct task_struct *get_current(void)
{
===== include/asm-arm/thread_info.h 1.8 vs edited =====
--- 1.8/include/asm-arm/thread_info.h Wed Sep 3 21:17:58 2003
+++ edited/include/asm-arm/thread_info.h Tue Jan 20 13:22:10 2004
@@ -76,7 +76,7 @@
/*
* how to get the thread information struct from C
*/
-static inline struct thread_info *current_thread_info(void) __attribute__ (( __const__ ));
+static inline struct thread_info *current_thread_info(void) __attribute_const__;

static inline struct thread_info *current_thread_info(void)
{
===== include/asm-arm26/current.h 1.1 vs edited =====
--- 1.1/include/asm-arm26/current.h Wed Jun 4 15:14:10 2003
+++ edited/include/asm-arm26/current.h Tue Jan 20 13:23:50 2004
@@ -3,7 +3,7 @@

#include <linux/thread_info.h>

-static inline struct task_struct *get_current(void) __attribute__ (( __const__ ));
+static inline struct task_struct *get_current(void) __attribute_const__;

static inline struct task_struct *get_current(void)
{
===== include/asm-arm26/thread_info.h 1.2 vs edited =====
--- 1.2/include/asm-arm26/thread_info.h Mon Jul 7 03:40:02 2003
+++ edited/include/asm-arm26/thread_info.h Tue Jan 20 13:23:50 2004
@@ -71,7 +71,7 @@
/*
* how to get the thread information struct from C
*/
-static inline struct thread_info *current_thread_info(void) __attribute__ (( __const__ ));
+static inline struct thread_info *current_thread_info(void) __attribute_const__;

static inline struct thread_info *current_thread_info(void)
{
===== include/asm-m68k/virtconvert.h 1.4 vs edited =====
--- 1.4/include/asm-m68k/virtconvert.h Mon Jan 19 09:35:43 2004
+++ edited/include/asm-m68k/virtconvert.h Tue Jan 20 13:13:07 2004
@@ -19,8 +19,8 @@
* Change virtual addresses to physical addresses and vv.
*/
#ifndef CONFIG_SUN3
-extern unsigned long mm_vtop(unsigned long addr) __attribute__ ((const));
-extern unsigned long mm_ptov(unsigned long addr) __attribute__ ((const));
+extern unsigned long mm_vtop(unsigned long addr) __attribute_const__;
+extern unsigned long mm_ptov(unsigned long addr) __attribute_const__;
#else
static inline unsigned long mm_vtop(unsigned long vaddr)
{
===== include/asm-ppc/io.h 1.14 vs edited =====
--- 1.14/include/asm-ppc/io.h Wed Sep 3 16:16:34 2003
+++ edited/include/asm-ppc/io.h Tue Jan 20 13:13:07 2004
@@ -208,7 +208,7 @@
#define ioremap_nocache(addr, size) ioremap((addr), (size))
extern void iounmap(void *addr);
extern unsigned long iopa(unsigned long addr);
-extern unsigned long mm_ptov(unsigned long addr) __attribute__ ((const));
+extern unsigned long mm_ptov(unsigned long addr) __attribute_const__;
extern void io_block_mapping(unsigned long virt, phys_addr_t phys,
unsigned int size, int flags);

===== include/asm-ppc/pgtable.h 1.27 vs edited =====
--- 1.27/include/asm-ppc/pgtable.h Mon Jan 19 09:35:58 2004
+++ edited/include/asm-ppc/pgtable.h Tue Jan 20 13:13:07 2004
@@ -626,7 +626,7 @@
extern void cache_push(__u32 addr, int length);
extern int mm_end_of_chunk (unsigned long addr, int len);
extern unsigned long iopa(unsigned long addr);
-extern unsigned long mm_ptov(unsigned long addr) __attribute__ ((const));
+extern unsigned long mm_ptov(unsigned long addr) __attribute_const__;

/* Values for nocacheflag and cmode */
/* These are not used by the APUS kernel_map, but prevents
===== include/asm-sparc/btfixup.h 1.2 vs edited =====
--- 1.2/include/asm-sparc/btfixup.h Thu Jun 6 10:08:28 2002
+++ edited/include/asm-sparc/btfixup.h Tue Jan 20 13:13:07 2004
@@ -39,7 +39,7 @@
extern __type ___f_##__name(__args); \
extern unsigned ___fs_##__name[3];
#define BTFIXUPDEF_CALL_CONST(__type, __name, __args...) \
- extern __type ___f_##__name(__args) __attribute__((const)); \
+ extern __type ___f_##__name(__args) __attribute_const__; \
extern unsigned ___fs_##__name[3];
#define BTFIXUP_CALL(__name) ___f_##__name

@@ -49,7 +49,7 @@
/* Put bottom 13bits into some register variable */

#define BTFIXUPDEF_SIMM13(__name) \
- extern unsigned int ___sf_##__name(void) __attribute__((const)); \
+ extern unsigned int ___sf_##__name(void) __attribute_const__; \
extern unsigned ___ss_##__name[2]; \
extern __inline__ unsigned int ___sf_##__name(void) { \
unsigned int ret; \
@@ -57,7 +57,7 @@
return ret; \
}
#define BTFIXUPDEF_SIMM13_INIT(__name,__val) \
- extern unsigned int ___sf_##__name(void) __attribute__((const)); \
+ extern unsigned int ___sf_##__name(void) __attribute_const__; \
extern unsigned ___ss_##__name[2]; \
extern __inline__ unsigned int ___sf_##__name(void) { \
unsigned int ret; \
@@ -71,7 +71,7 @@
*/

#define BTFIXUPDEF_HALF(__name) \
- extern unsigned int ___af_##__name(void) __attribute__((const)); \
+ extern unsigned int ___af_##__name(void) __attribute_const__; \
extern unsigned ___as_##__name[2]; \
extern __inline__ unsigned int ___af_##__name(void) { \
unsigned int ret; \
@@ -79,7 +79,7 @@
return ret; \
}
#define BTFIXUPDEF_HALF_INIT(__name,__val) \
- extern unsigned int ___af_##__name(void) __attribute__((const)); \
+ extern unsigned int ___af_##__name(void) __attribute_const__; \
extern unsigned ___as_##__name[2]; \
extern __inline__ unsigned int ___af_##__name(void) { \
unsigned int ret; \
@@ -90,7 +90,7 @@
/* Put upper 22 bits into some register variable */

#define BTFIXUPDEF_SETHI(__name) \
- extern unsigned int ___hf_##__name(void) __attribute__((const)); \
+ extern unsigned int ___hf_##__name(void) __attribute_const__; \
extern unsigned ___hs_##__name[2]; \
extern __inline__ unsigned int ___hf_##__name(void) { \
unsigned int ret; \
@@ -98,7 +98,7 @@
return ret; \
}
#define BTFIXUPDEF_SETHI_INIT(__name,__val) \
- extern unsigned int ___hf_##__name(void) __attribute__((const)); \
+ extern unsigned int ___hf_##__name(void) __attribute_const__; \
extern unsigned ___hs_##__name[2]; \
extern __inline__ unsigned int ___hf_##__name(void) { \
unsigned int ret; \
===== include/asm-sparc/pgtable.h 1.17 vs edited =====
--- 1.17/include/asm-sparc/pgtable.h Thu Oct 2 11:11:59 2003
+++ edited/include/asm-sparc/pgtable.h Tue Jan 20 13:13:07 2004
@@ -80,7 +80,7 @@
BTFIXUPDEF_SETHI(pmd_size)
BTFIXUPDEF_SETHI(pmd_mask)

-extern unsigned int pmd_align(unsigned int addr) __attribute__((const));
+extern unsigned int pmd_align(unsigned int addr) __attribute_const__;
extern __inline__ unsigned int pmd_align(unsigned int addr)
{
return ((addr + ~BTFIXUP_SETHI(pmd_mask)) & BTFIXUP_SETHI(pmd_mask));
@@ -90,7 +90,7 @@
BTFIXUPDEF_SETHI(pgdir_size)
BTFIXUPDEF_SETHI(pgdir_mask)

-extern unsigned int pgdir_align(unsigned int addr) __attribute__((const));
+extern unsigned int pgdir_align(unsigned int addr) __attribute_const__;
extern __inline__ unsigned int pgdir_align(unsigned int addr)
{
return ((addr + ~BTFIXUP_SETHI(pgdir_mask)) & BTFIXUP_SETHI(pgdir_mask));
@@ -248,19 +248,19 @@
BTFIXUPDEF_HALF(pte_dirtyi)
BTFIXUPDEF_HALF(pte_youngi)

-extern int pte_write(pte_t pte) __attribute__((const));
+extern int pte_write(pte_t pte) __attribute_const__;
extern __inline__ int pte_write(pte_t pte)
{
return pte_val(pte) & BTFIXUP_HALF(pte_writei);
}

-extern int pte_dirty(pte_t pte) __attribute__((const));
+extern int pte_dirty(pte_t pte) __attribute_const__;
extern __inline__ int pte_dirty(pte_t pte)
{
return pte_val(pte) & BTFIXUP_HALF(pte_dirtyi);
}

-extern int pte_young(pte_t pte) __attribute__((const));
+extern int pte_young(pte_t pte) __attribute_const__;
extern __inline__ int pte_young(pte_t pte)
{
return pte_val(pte) & BTFIXUP_HALF(pte_youngi);
@@ -271,7 +271,7 @@
*/
BTFIXUPDEF_HALF(pte_filei)

-extern int pte_file(pte_t pte) __attribute__((const));
+extern int pte_file(pte_t pte) __attribute_const__;
extern __inline__ int pte_file(pte_t pte)
{
return pte_val(pte) & BTFIXUP_HALF(pte_filei);
@@ -283,19 +283,19 @@
BTFIXUPDEF_HALF(pte_mkcleani)
BTFIXUPDEF_HALF(pte_mkoldi)

-extern pte_t pte_wrprotect(pte_t pte) __attribute__((const));
+extern pte_t pte_wrprotect(pte_t pte) __attribute_const__;
extern __inline__ pte_t pte_wrprotect(pte_t pte)
{
return __pte(pte_val(pte) & ~BTFIXUP_HALF(pte_wrprotecti));
}

-extern pte_t pte_mkclean(pte_t pte) __attribute__((const));
+extern pte_t pte_mkclean(pte_t pte) __attribute_const__;
extern __inline__ pte_t pte_mkclean(pte_t pte)
{
return __pte(pte_val(pte) & ~BTFIXUP_HALF(pte_mkcleani));
}

-extern pte_t pte_mkold(pte_t pte) __attribute__((const));
+extern pte_t pte_mkold(pte_t pte) __attribute_const__;
extern __inline__ pte_t pte_mkold(pte_t pte)
{
return __pte(pte_val(pte) & ~BTFIXUP_HALF(pte_mkoldi));
@@ -332,7 +332,7 @@

BTFIXUPDEF_INT(pte_modify_mask)

-extern pte_t pte_modify(pte_t pte, pgprot_t newprot) __attribute__((const));
+extern pte_t pte_modify(pte_t pte, pgprot_t newprot) __attribute_const__;
extern __inline__ pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
return __pte((pte_val(pte) & BTFIXUP_INT(pte_modify_mask)) |
===== include/linux/reiserfs_fs.h 1.53 vs edited =====
--- 1.53/include/linux/reiserfs_fs.h Tue Dec 30 11:44:59 2003
+++ edited/include/linux/reiserfs_fs.h Tue Jan 20 13:23:50 2004
@@ -90,7 +90,7 @@
#define RFALSE( cond, format, args... ) do {;} while( 0 )
#endif

-#define CONSTF __attribute__( ( const ) )
+#define CONSTF __attribute_const__
/*
* Disk Data Structures
*/
-
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