Re: [PATCH 2/3][mdadm] mdadm.h: bswap is already defined in uclibc

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"Maxin B. John" <maxin.john@xxxxxxxxx> writes:
> Hi Jes,
>
> On Mon, Feb 8, 2016 at 6:00 PM, Jes Sorensen <Jes.Sorensen@xxxxxxxxxx> wrote:
>> "Maxin B. John" <maxin.john@xxxxxxxxx> writes:
>>> From: "Maxin B. John" <maxin.john@xxxxxxxxx>
>>>
>>> Fixes this build error:
>>>
>>> | In file included from mdadm.c:28:0:
>>> | mdadm.h:142:0: error: "bswap_16" redefined [-Werror]
>>> |  #define bswap_16(x) (((x) & 0x00ffU) << 8 | \
>>> |  ^
>>>
>>> Signed-off-by: Maxin B. John <maxin.john@xxxxxxxxx>
>>> ---
>>>  mdadm.h | 9 +++++++++
>>>  1 file changed, 9 insertions(+)
>>
>> Hi Maxin,
>>
>> I am not opposed to this, but I would like to understand why you see
>> these duplicate defines. What defines it in your build environment?
>
>
> I get the below listed error message with uclibc builds:

<ship>

> | In file included from mdadm.c:28:0:
> | mdadm.h:142:0: error: "bswap_16" redefined [-Werror]
> |  #define bswap_16(x) (((x) & 0x00ffU) << 8 | \
> |  ^
> | In file included from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/endian.h:59:0,
> |                  from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/sys/types.h:216,
> |                  from mdadm.h:36,
> |                  from mdadm.c:28:
> | /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/byteswap.h:29:0:
> note: this is the location of the previous definition
> |  #define bswap_16(x) __bswap_16 (x)
> |  ^
> | In file included from mdadm.c:28:0:
> | mdadm.h:144:0: error: "bswap_32" redefined [-Werror]
> |  #define bswap_32(x) (((x) & 0x000000ffU) << 24 | \
> |  ^
> | In file included from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/endian.h:59:0,
> |                  from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/sys/types.h:216,
> |                  from mdadm.h:36,
> |                  from mdadm.c:28:
> | /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/byteswap.h:32:0:
> note: this is the location of the previous definition
> |  #define bswap_32(x) __bswap_32 (x)
> |  ^
> | In file included from mdadm.c:28:0:
> | mdadm.h:148:0: error: "bswap_64" redefined [-Werror]
> |  #define bswap_64(x) (((x) & 0x00000000000000ffULL) << 56 | \
> |  ^
> | In file included from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/endian.h:59:0,
> |                  from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/sys/types.h:216,
> |                  from mdadm.h:36,
> |                  from mdadm.c:28:
> | /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/byteswap.h:36:0:
> note: this is the location of the previous definition
> |  # define bswap_64(x) __bswap_64 (x)
> |  ^
> | In file included from config.c:25:0:
> | mdadm.h:142:0: error: "bswap_16" redefined [-Werror]
> |  #define bswap_16(x) (((x) & 0x00ffU) << 8 | \
> |  ^
> | In file included from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/endian.h:59:0,
> |                  from
> /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/sys/types.h:216,
> |                  from mdadm.h:36,
> |                  from config.c:25:
> | /home/maxin/poky/build/tmp/sysroots/qemux86-64/usr/include/byteswap.h:29:0:
> note: this is the location of the previous definition
> |  #define bswap_16(x) __bswap_16 (x)
> |  ^
> ......

Maxin,

I think it's actually wrong for uClibc to expose those macros with such
a common name, but rather than picking up outside macros randomly I
prefer to rename the mdadm ones to be sure we know what we are getting.

Instead of your patch, I applied this one instead. I hope that is fine
with you.

Cheers,
Jes

>From dd47b4e0c45fd72b94a9a7d0f0a5046ef9c8d97b Mon Sep 17 00:00:00 2001
From: Jes Sorensen <Jes.Sorensen@xxxxxxxxxx>
Date: Wed, 10 Feb 2016 14:15:38 -0500
Subject: [PATCH] mdadm.h: rename bswap macros to avoid clash with uClibc
 definitions

uClibc exposes it's own version of bswap_<X> macros. Rather than
pulling in random macros by change, rename the mdadm ones to make sure
we know what we are getting.

Reported-by: "Maxin B. John" <maxin.john@xxxxxxxxx>
Signed-off-by: Jes Sorensen <Jes.Sorensen@xxxxxxxxxx>
---
 mdadm.h | 52 ++++++++++++++++++++++++++--------------------------
 1 file changed, 26 insertions(+), 26 deletions(-)

diff --git a/mdadm.h b/mdadm.h
index dd02be7..72888e2 100755
--- a/mdadm.h
+++ b/mdadm.h
@@ -139,20 +139,20 @@ struct dlm_lksb {
  * and there is no standard conversion function so... */
 /* And dietlibc doesn't think byteswap is ok, so.. */
 /*  #include <byteswap.h> */
-#define bswap_16(x) (((x) & 0x00ffU) << 8 | \
-		     ((x) & 0xff00U) >> 8)
-#define bswap_32(x) (((x) & 0x000000ffU) << 24 | \
-		     ((x) & 0xff000000U) >> 24 | \
-		     ((x) & 0x0000ff00U) << 8  | \
-		     ((x) & 0x00ff0000U) >> 8)
-#define bswap_64(x) (((x) & 0x00000000000000ffULL) << 56 | \
-		     ((x) & 0xff00000000000000ULL) >> 56 | \
-		     ((x) & 0x000000000000ff00ULL) << 40 | \
-		     ((x) & 0x00ff000000000000ULL) >> 40 | \
-		     ((x) & 0x0000000000ff0000ULL) << 24 | \
-		     ((x) & 0x0000ff0000000000ULL) >> 24 | \
-		     ((x) & 0x00000000ff000000ULL) << 8 | \
-		     ((x) & 0x000000ff00000000ULL) >> 8)
+#define __mdadm_bswap_16(x) (((x) & 0x00ffU) << 8 | \
+			     ((x) & 0xff00U) >> 8)
+#define __mdadm_bswap_32(x) (((x) & 0x000000ffU) << 24 | \
+			     ((x) & 0xff000000U) >> 24 | \
+			     ((x) & 0x0000ff00U) << 8  | \
+			     ((x) & 0x00ff0000U) >> 8)
+#define __mdadm_bswap_64(x) (((x) & 0x00000000000000ffULL) << 56 | \
+			     ((x) & 0xff00000000000000ULL) >> 56 | \
+			     ((x) & 0x000000000000ff00ULL) << 40 | \
+			     ((x) & 0x00ff000000000000ULL) >> 40 | \
+			     ((x) & 0x0000000000ff0000ULL) << 24 | \
+			     ((x) & 0x0000ff0000000000ULL) >> 24 | \
+			     ((x) & 0x00000000ff000000ULL) << 8 |  \
+			     ((x) & 0x000000ff00000000ULL) >> 8)
 
 #if !defined(__KLIBC__)
 #if BYTE_ORDER == LITTLE_ENDIAN
@@ -163,19 +163,19 @@ struct dlm_lksb {
 #define __le32_to_cpu(_x) (unsigned int)(_x)
 #define __le64_to_cpu(_x) (unsigned long long)(_x)
 
-#define	__cpu_to_be16(_x) bswap_16(_x)
-#define __cpu_to_be32(_x) bswap_32(_x)
-#define __cpu_to_be64(_x) bswap_64(_x)
-#define	__be16_to_cpu(_x) bswap_16(_x)
-#define __be32_to_cpu(_x) bswap_32(_x)
-#define __be64_to_cpu(_x) bswap_64(_x)
+#define	__cpu_to_be16(_x) __mdadm_bswap_16(_x)
+#define __cpu_to_be32(_x) __mdadm_bswap_32(_x)
+#define __cpu_to_be64(_x) __mdadm_bswap_64(_x)
+#define	__be16_to_cpu(_x) __mdadm_bswap_16(_x)
+#define __be32_to_cpu(_x) __mdadm_bswap_32(_x)
+#define __be64_to_cpu(_x) __mdadm_bswap_64(_x)
 #elif BYTE_ORDER == BIG_ENDIAN
-#define	__cpu_to_le16(_x) bswap_16(_x)
-#define __cpu_to_le32(_x) bswap_32(_x)
-#define __cpu_to_le64(_x) bswap_64(_x)
-#define	__le16_to_cpu(_x) bswap_16(_x)
-#define __le32_to_cpu(_x) bswap_32(_x)
-#define __le64_to_cpu(_x) bswap_64(_x)
+#define	__cpu_to_le16(_x) __mdadm_bswap_16(_x)
+#define __cpu_to_le32(_x) __mdadm_bswap_32(_x)
+#define __cpu_to_le64(_x) __mdadm_bswap_64(_x)
+#define	__le16_to_cpu(_x) __mdadm_bswap_16(_x)
+#define __le32_to_cpu(_x) __mdadm_bswap_32(_x)
+#define __le64_to_cpu(_x) __mdadm_bswap_64(_x)
 
 #define	__cpu_to_be16(_x) (unsigned int)(_x)
 #define __cpu_to_be32(_x) (unsigned int)(_x)
-- 
2.5.0

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