linux-kernel - [RFC][PATCH] A generic boolean

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Date:	Wed, 19 Jul 2006 22:38:20 +0200
From:	ricknu-0@...dent.ltu.se
To:	linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] A generic boolean

From: Richard Knutsson

A first step to a generic boolean-type. The patch just introduce the bool (in
arch. i386 only (for the moment)), false and true + fixing some duplications in
the code.
It is diffed against Linus' git-tree (060718)
Compiled with my own-, allyesconfig- and allmodconfig-config.h-file.

-Why would we want it?
-There is already some how are depending on a "boolean"-type (like NTFS). Also,
it will clearify functions who returns a boolean from one returning a value, ex:
bool it_is_ok();
char it_is_ok();
The first one is obvious what it is doing, the secound might return some sort of
status.

-Why false and not FALSE, why not "enum {...} bool"
-They are not #define(d) and shouldn't because it is a value, like 'a'. But
because it is just a value, then bool is just a variable and should be able to
handle 0 and 1 equally well.

Well, this is _my_ opinion, it may be totally wrong. If so, please tell me ;)

If this takes off, I guess I will spend quite some time at kernel-janitors
"cleaning" those who use a boolean-type.

Til' next time...
/Richard Knutsson

PS
Yes, I know about Andrew's try to unify TRUE and FALSE, did read the thread with
interest (that's from where I got to know about _Bool). But mostly (then still
on the subject) was some people did not want FALSE and TRUE instead of 0 and 1.
I look at it as: 'a' = 97, if someone like to write 97 instead of 'a', please do
if you find it easier to read. I, on the other hand, think it is easier with
'a', false/FALSE, NULL, etc.
DS

PPS
One thing about _Bool thue:
_Bool a = 12; results in a = 1

test( char * t ) { t = 12; }
main() {
_Bool a;
test( (char *) &a ); results in a = 12.
}

But I do not think of it as a problem since a "true" is just !false. Doing:
if (boolvar == true)
seems odd, after all...

... and sorry for the longwinded letter :)
DDS

Signed-off-by: Richard Knutsson <ricknu-0@...dent.ltu.se>

---

 drivers/block/DAC960.h            |    2 +-
 drivers/media/video/cpia2/cpia2.h |    4 ----
 drivers/net/dgrs.c                |    1 -
 drivers/scsi/BusLogic.h           |    5 +----
 include/asm-i386/types.h          |    9 +++++++++
 include/linux/stddef.h            |    2 ++
 6 files changed, 13 insertions(+), 10 deletions(-)



diff --git a/drivers/block/DAC960.h b/drivers/block/DAC960.h
index a82f37f..f9217c3 100644
--- a/drivers/block/DAC960.h
+++ b/drivers/block/DAC960.h
@@ -71,7 +71,7 @@ #define DAC690_V2_PciDmaMask	0xfffffffff
   Define a Boolean data type.
 */
 
-typedef enum { false, true } __attribute__ ((packed)) boolean;
+typedef bool boolean;
 
 
 /*
diff --git a/drivers/media/video/cpia2/cpia2.h b/drivers/media/video/cpia2/cpia2.h
index c5ecb2b..8d2dfc1 100644
--- a/drivers/media/video/cpia2/cpia2.h
+++ b/drivers/media/video/cpia2/cpia2.h
@@ -50,10 +50,6 @@ #define CPIA2_PATCH_VER	0
 /***
  * Image defines
  ***/
-#ifndef true
-#define true 1
-#define false 0
-#endif
 
 /*  Misc constants */
 #define ALLOW_CORRUPT 0		/* Causes collater to discard checksum */
diff --git a/drivers/net/dgrs.c b/drivers/net/dgrs.c
index fa4f094..4dbc23d 100644
--- a/drivers/net/dgrs.c
+++ b/drivers/net/dgrs.c
@@ -110,7 +110,6 @@ static char version[] __initdata =
  *	DGRS include files
  */
 typedef unsigned char uchar;
-typedef unsigned int bool;
 #define vol volatile
 
 #include "dgrs.h"
diff --git a/drivers/scsi/BusLogic.h b/drivers/scsi/BusLogic.h
index 9792e5a..d6d1d56 100644
--- a/drivers/scsi/BusLogic.h
+++ b/drivers/scsi/BusLogic.h
@@ -237,10 +237,7 @@ enum BusLogic_BIOS_DiskGeometryTranslati
   Define a Boolean data type.
 */
 
-typedef enum {
-	false,
-	true
-} PACKED boolean;
+typedef bool boolean;
 
 /*
   Define a 10^18 Statistics Byte Counter data type.
diff --git a/include/asm-i386/types.h b/include/asm-i386/types.h
index 4b4b295..e35709a 100644
--- a/include/asm-i386/types.h
+++ b/include/asm-i386/types.h
@@ -10,6 +10,15 @@ typedef unsigned short umode_t;
  * header files exported to user space
  */
 
+#if defined(__GNUC__) && __GNUC__ >= 3
+typedef _Bool bool;
+#else
+#warning You compiler doesn't seem to support boolean types, will set 'bool' as
an 'unsigned char'
+typedef unsigned char bool;
+#endif
+
+typedef bool u2;
+
 typedef __signed__ char __s8;
 typedef unsigned char __u8;
 
diff --git a/include/linux/stddef.h b/include/linux/stddef.h
index b3a2cad..5e5c611 100644
--- a/include/linux/stddef.h
+++ b/include/linux/stddef.h
@@ -10,6 +10,8 @@ #else
 #define NULL ((void *)0)
 #endif
 
+enum { false = 0, true = 1 } __attribute__((packed));
+
 #undef offsetof
 #ifdef __compiler_offsetof
 #define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER)

-
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