On Tue, Sep 15 2015, Andrew Morton wrote:
> On Mon, 14 Sep 2015 23:46:32 -0400 Tejun Heo <t...@kernel.org> wrote:
>
>> Anyways, let's please get abs() working for all types, one way or the
>> other.
>
> That would be by far the best solution, of course.
>
> This seems to work OK:
>
> --- a/include/linux/kernel.h~a
> +++ a/include/linux/kernel.h
> @@ -207,8 +207,11 @@ extern int _cond_resched(void);
> * for those.
> */
> #define abs(x) ({ \
> - long ret; \
> - if (sizeof(x) == sizeof(long)) { \
> + s64 ret; \
> + if (sizeof(x) == sizeof(s64)) { \
> + s64 __x = (x); \
> + ret = (__x < 0) ? -__x : __x; \
> + } else if (sizeof(x) == sizeof(long)) { \
> long __x = (x); \
> ret = (__x < 0) ? -__x : __x; \
> } else { \
If the return type is an issue, we can use __builtin_choose_expr, no?
#define abs(x) __builtin_choose_expr(sizeof(x) == sizeof(s64), abs64(x), ({ \
long ret; \
if (sizeof(x) == sizeof(long)) { \
long __x = (x); \
ret = (__x < 0) ? -__x : __x; \
} else { \
int __x = (x); \
ret = (__x < 0) ? -__x : __x; \
} \
ret; \
}))
This is awkward but will make even printk happy.
>
> Test case:
>
> --- /dev/null
> +++ a/lib/xx.c
> @@ -0,0 +1,33 @@
> +#include <linux/kernel.h>
> +
> +#define newabs(x) ({ \
> + s64 ret; \
> + if (sizeof(x) == sizeof(s64)) { \
> + s64 __x = (x); \
> + ret = (__x < 0) ? -__x : __x; \
> + } else if (sizeof(x) == sizeof(long)) { \
> + long __x = (x); \
> + ret = (__x < 0) ? -__x : __x; \
> + } else { \
> + int __x = (x); \
> + ret = (__x < 0) ? -__x : __x; \
> + } \
> + ret; \
> + })
> +
> +#define oldabs(x) ({ \
> + long ret; \
> + if (sizeof(x) == sizeof(long)) { \
> + long __x = (x); \
> + ret = (__x < 0) ? -__x : __x; \
> + } else { \
> + int __x = (x); \
> + ret = (__x < 0) ? -__x : __x; \
> + } \
> + ret; \
> + })
> +
> +int foo(int x)
> +{
> + return oldabs(x);
> +}
> diff -puN lib/Makefile~b lib/Makefile
> --- a/lib/Makefile~b
> +++ a/lib/Makefile
> @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmd
> sha1.o md5.o irq_regs.o argv_split.o \
> proportions.o flex_proportions.o ratelimit.o show_mem.o \
> is_single_threaded.o plist.o decompress.o kobject_uevent.o \
> - earlycpio.o seq_buf.o nmi_backtrace.o
> + earlycpio.o seq_buf.o nmi_backtrace.o xx.o
>
> obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
> lib-$(CONFIG_MMU) += ioremap.o
>
>
> on i386, xx.o's text is 68 bytes with either newabs() or oldabs().
>
>
> lib/percpu_counter.o's text does get larger with newabs(). That's
> because __percpu_counter_compare() is doing abs() on an s64, doh.
>
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, ミハウ “mina86” ナザレヴイツ (o o)
ooo +--<m...@google.com>--<xmpp:min...@jabber.org>-----ooO--(_)--Ooo--
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