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[Qemu-devel] [PULL v4 05/23] compiler: rework BUG_ON using a struct
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PULL v4 05/23] compiler: rework BUG_ON using a struct |
Date: |
Tue, 31 Jan 2017 20:42:57 +0200 |
There are theoretical concerns that some compilers might not trigger
build failures on attempts to define an array of size (x ? -1 : 1) where
x is a variable and make it a variable sized array instead. Let rewrite
using a struct with a negative bit field size instead as there are no
dynamic bit field sizes. This is similar to what Linux does.
Signed-off-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Markus Armbruster <address@hidden>
---
include/qemu/compiler.h | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 77b9ce3..057639a 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -85,10 +85,14 @@
#define typeof_field(type, field) typeof(((type *)0)->field)
#define type_check(t1,t2) ((t1*)0 - (t2*)0)
+#define QEMU_BUILD_BUG_ON_STRUCT(x) \
+ struct { \
+ int:(x) ? -1 : 1; \
+ }
+
#ifdef __COUNTER__
-#define QEMU_BUILD_BUG_ON(x) \
- typedef char glue(qemu_build_bug_on__, __COUNTER__)[(x) ? -1 : 1] \
- __attribute__((unused))
+#define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
+ glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
#else
#define QEMU_BUILD_BUG_ON(x)
#endif
--
MST
- [Qemu-devel] [PULL v4 00/23] virtio, vhost, pci: fixes, features, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 01/23] compiler: drop ; after BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 02/23] qxl: switch to constants within BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 03/23] ppc: switch to constants within BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 05/23] compiler: rework BUG_ON using a struct,
Michael S. Tsirkin <=
- [Qemu-devel] [PULL v4 04/23] QEMU_BUILD_BUG_ON: use __COUNTER__, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 06/23] QEMU_BUILD_BUG_ON: use __COUNTER__, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 08/23] ARRAY_SIZE: check that argument is an array, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 07/23] compiler: expression version of QEMU_BUILD_BUG_ON, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 09/23] pci: mark ROMs read-only, Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 10/23] intel_iommu: fix and simplify size calculation in process_device_iotlb_desc(), Michael S. Tsirkin, 2017/01/31
- [Qemu-devel] [PULL v4 12/23] hw/ioh3420: derive from PCI Express Root Port base class, Michael S. Tsirkin, 2017/01/31