Xen devel - Dec 2011 - [PATCH] blktap2: use HAVE_BYTESWAP_H and _BYTESWAP_H for uclibc compatibility

# HG changeset patch
# User Roger Pau Monne <roger.pau@entel.upc.edu>
# Date 1323969492 -3600
# Node ID a01f1e2f654ea54bbf5d0a77b315b676cc494aa8
# Parent  0051e09f73efea06f2f28c0ece57194e286daedc
blktap2: use HAVE_BYTESWAP_H and _BYTESWAP_H for uclibc compatibility

uclibc defines _BYTESWAP_H instead of HAVE_BYTESWAP_H in byteswap.h:

http://git.uclibc.org/uClibc/tree/include/byteswap.h

Without this fix, blktap2 doesn''t compile under uclibc and throws the
following error:

gcc  -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing
-std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement
-Wno-unused-but-set-variable   -D__XEN_TOOLS__ -MMD -MF
.block-qcow.o.d  -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
-fno-optimize-sibling-calls -Werror -g -O0 -Wno-unused
-fno-strict-aliasing -I../include -I../drivers
-I/root/xen-unstable/tools/blktap2/drivers/../../../tools/libxc
-I/root/xen-unstable/tools/blktap2/drivers/../../../tools/include -I
/root/xen-unstable/tools/blktap2/drivers/../../../tools/memshr
-D_GNU_SOURCE -DUSE_NFS_LOCKS -fPIC -I
/root/xen-unstable/tools/blktap2/drivers/../../../tools/libaio/src  -c
-o block-qcow.o block-qcow.c  -I/usr/local/include
In file included from block-qcow.c:37:0:
bswap.h:23:0: error: "bswap_16" redefined [-Werror]
/usr/include/byteswap.h:30:0: note: this is the location of the
previous definition
bswap.h:31:0: error: "bswap_32" redefined [-Werror]
/usr/include/byteswap.h:33:0: note: this is the location of the
previous definition
bswap.h:41:0: error: "bswap_64" redefined [-Werror]
/usr/include/byteswap.h:37:0: note: this is the location of the
previous definition
cc1: all warnings being treated as errors

Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>

diff -r 0051e09f73ef -r a01f1e2f654e tools/blktap2/drivers/bswap.h
--- a/tools/blktap2/drivers/bswap.h	Thu Dec 15 10:00:09 2011 +0100
+++ b/tools/blktap2/drivers/bswap.h	Thu Dec 15 18:18:12 2011 +0100
@@ -15,7 +15,7 @@
 #define bswap_64(x) swap64(x)
 #else
 
-#ifdef HAVE_BYTESWAP_H
+#if defined(HAVE_BYTESWAP_H) || defined(_BYTESWAP_H)
 #include <byteswap.h>
 #else

I''m having second thoughts about this patch, although it works,
I''m
not sure it''s the right way to do it. I don''t know why
configure fails
to set HAVE_BYTESWAP_H when using uclibc. Any thoughts?

This patch is wrong, but I think blktap bswap.h is also wrong, because
HAVE_BYTESWAP_H is defined by qemu, but blktap doesn''t include qemu
config file, so HAVE_BYTESWAP_H is not defined in this header file
(which doesn''t mean that byteswap.h is not present on the system). How
should we fix this? Forget about including byteswap.h and always
define the functions ourselves?

Thanks, Roger.

On Fri, 2011-12-16 at 13:19 +0000, Roger Pau Monné
wrote:
> This patch is wrong, but I think blktap bswap.h is also wrong, because
> HAVE_BYTESWAP_H is defined by qemu, but blktap doesn't include qemu
> config file, so HAVE_BYTESWAP_H is not defined in this header file
> (which doesn't mean that byteswap.h is not present on the system). How
> should we fix this? Forget about including byteswap.h and always
> define the functions ourselves?
If HAVE_BYTESWAP_H has never been defined up until now can't we just
delete the include?
> 
> Thanks, Roger.
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel


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