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[Qemu-devel] [PATCH v3 2/4] compiler: rework BUG_ON using a struct
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PATCH v3 2/4] compiler: rework BUG_ON using a struct |
Date: |
Thu, 19 Jan 2017 23:07:29 +0200 |
There are theoretical concerns that some compilers might not trigger
build failures on attempts to define an array of size -1 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>
---
include/qemu/compiler.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 7512082..c6f673e 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -85,9 +85,12 @@
#define typeof_field(type, field) typeof(((type *)0)->field)
#define type_check(t1,t2) ((t1*)0 - (t2*)0)
-#define QEMU_BUILD_BUG_ON(x) \
- typedef char glue(qemu_build_bug_on__, __LINE__)[(x) ? -1 : 1] \
- __attribute__((unused))
+#define QEMU_BUILD_BUG_ON_STRUCT(x) \
+ struct { \
+ int qemu_build_bug_on : (x) ? -1 : 1; \
+ }
+#define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
+ glue(qemu_build_bug_on__, __LINE__) __attribute__((unused))
#if defined __GNUC__
# if !QEMU_GNUC_PREREQ(4, 4)
--
MST
Re: [Qemu-devel] [PATCH v3 2/4] compiler: rework BUG_ON using a struct, Dr. David Alan Gilbert, 2017/01/20