[Xen-devel] [PATCH v2] x86/compat: fix compilation errors with clang 6

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

The following errors are generated when compiling Xen with clang 6:

In file included from x86_64/asm-offsets.c:9:
In file included from /root/src/xen/xen/include/xen/sched.h:8:
In file included from /root/src/xen/xen/include/xen/shared.h:6:
In file included from /root/src/xen/xen/include/compat/arch-x86/../xen.h:9:
/root/src/xen/xen/include/compat/arch-x86/xen.h:10:10: error: the current 
#pragma pack aligment
      value is modified in the included file [-Werror,-Wpragma-pack]
#include "xen-x86_32.h"
         ^
/root/src/xen/xen/include/compat/arch-x86/xen-x86_32.h:40:9: note: previous 
'#pragma pack'
      directive that modifies alignment is here
#pragma pack()
        ^
In file included from x86_64/asm-offsets.c:9:
In file included from /root/src/xen/xen/include/xen/sched.h:8:
In file included from /root/src/xen/xen/include/xen/shared.h:6:
/root/src/xen/xen/include/compat/arch-x86/../xen.h:9:10: error: the current 
#pragma pack aligment
      value is modified in the included file [-Werror,-Wpragma-pack]
#include "arch-x86/xen.h"
         ^
/root/src/xen/xen/include/compat/arch-x86/xen.h:71:9: note: previous '#pragma 
pack' directive that
      modifies alignment is here
#pragma pack()
        ^
2 errors generated.

Fix this by using pragma push/pop in order to store the current pragma
value in the compiler stack and later restoring it when using clang.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
Changes since v1:
 - Only use push/pop with clang.
---
 xen/include/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xen/include/Makefile b/xen/include/Makefile
index 1299b1962f..19066a33a0 100644
--- a/xen/include/Makefile
+++ b/xen/include/Makefile
@@ -35,8 +35,13 @@ cppflags-y                := -include public/xen-compat.h 
-DXEN_GENERATING_COMPA
 cppflags-$(CONFIG_X86)    += -m32
 
 # 8-byte types are 4-byte aligned on x86_32 ...
+ifeq ($(clang),y)
+prefix-$(CONFIG_X86)      := \#pragma pack(push, 4)
+suffix-$(CONFIG_X86)      := \#pragma pack(pop)
+else
 prefix-$(CONFIG_X86)      := \#pragma pack(4)
 suffix-$(CONFIG_X86)      := \#pragma pack()
+endif
 
 endif
 
-- 
2.15.1


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