The patch titled
Subject: include/linux/compiler.h: fix C++ uninitialized const issue
has been added to the -mm tree. Its filename is
compilerh-fix-c-uninitialized-const-issue.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/compilerh-fix-c-uninitialized-const-issue.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/compilerh-fix-c-uninitialized-const-issue.patch
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------------------------------------------------------
From: Joakim Tjernlund <joakim.tjernlund@xxxxxxxxxxxx>
Subject: include/linux/compiler.h: fix C++ uninitialized const issue
C++ does not like the union { typeof(x) __val; char __c[1]; } __u
construct for const types:
error: uninitialized const member in
'union atomic_read(const atomic_t*)::<anonymous>'
Address this by creating a C++ version of READ_ONCE where this union is
initialized: union { void _u(){}; typeof(x) __val; char __c[1]; } __u={0}
To please gcc 6.3.0 also add in a _u(){} as default ctor.
This makes C++ happy enough to build.
Link: http://lkml.kernel.org/r/20170221151044.5499-2-joakim.tjernlund@xxxxxxxxxxxx
Signed-off-by: Joakim Tjernlund <joakim.tjernlund@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/compiler.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff -puN include/linux/compiler.h~compilerh-fix-c-uninitialized-const-issue include/linux/compiler.h
--- a/include/linux/compiler.h~compilerh-fix-c-uninitialized-const-issue
+++ a/include/linux/compiler.h
@@ -311,6 +311,7 @@ static __always_inline void __write_once
* required ordering.
*/
+#ifndef __cplusplus
#define __READ_ONCE(x, check) \
({ \
union { typeof(x) __val; char __c[1]; } __u; \
@@ -320,6 +321,17 @@ static __always_inline void __write_once
__read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
__u.__val; \
})
+#else
+#define __READ_ONCE(x, check) \
+({ \
+ union { void _u(){}; typeof(x) __val; char __c[1]; } __u={0}; \
+ if (check) \
+ __read_once_size(&(x), __u.__c, sizeof(x)); \
+ else \
+ __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
+ __u.__val; \
+})
+#endif
#define READ_ONCE(x) __READ_ONCE(x, 1)
/*
_
Patches currently in -mm which might be from joakim.tjernlund@xxxxxxxxxxxx are
correct-function-definition-for-c.patch
compilerh-fix-c-uninitialized-const-issue.patch
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