Subject: + compilerh-avoid-sparse-errors-in-__compiletime_error_fallback.patch added to -mm tree
To: james.hogan@xxxxxxxxxx,daniel.santos@xxxxxxxxx,johannes.berg@xxxxxxxxx,johannes@xxxxxxxxxxxxxxxx,luciano.coelho@xxxxxxxxx,paulmck@xxxxxxxxxxxxxxxxxx,peterz@xxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 15 May 2014 16:03:24 -0700
The patch titled
Subject: compiler.h: avoid sparse errors in __compiletime_error_fallback()
has been added to the -mm tree. Its filename is
compilerh-avoid-sparse-errors-in-__compiletime_error_fallback.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/compilerh-avoid-sparse-errors-in-__compiletime_error_fallback.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/compilerh-avoid-sparse-errors-in-__compiletime_error_fallback.patch
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From: James Hogan <james.hogan@xxxxxxxxxx>
Subject: compiler.h: avoid sparse errors in __compiletime_error_fallback()
Usually, BUG_ON and friends aren't even evaluated in sparse, but recently
compiletime_assert_atomic_type() was added, and that now results in a
sparse warning every time it is used.
The reason turns out to be the temporary variable, after it sparse no
longer considers the value to be a constant, and results in a warning and
an error. The error is the more annoying part of this as it suppresses
any further warnings in the same file, hiding other problems.
Unfortunately the condition cannot be simply expanded out to avoid the
temporary variable since it breaks compiletime_assert on old versions of
GCC such as GCC 4.2.4 which the latest metag compiler is based on.
Therefore #ifndef __CHECKER__ out the __compiletime_error_fallback which
uses the potentially negative size array to trigger a conditional compiler
error, so that sparse doesn't see it.
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Johannes Berg <johannes.berg@xxxxxxxxx>
Cc: Daniel Santos <daniel.santos@xxxxxxxxx>
Cc: Luciano Coelho <luciano.coelho@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Acked-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/compiler.h | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff -puN include/linux/compiler.h~compilerh-avoid-sparse-errors-in-__compiletime_error_fallback include/linux/compiler.h
--- a/include/linux/compiler.h~compilerh-avoid-sparse-errors-in-__compiletime_error_fallback
+++ a/include/linux/compiler.h
@@ -323,9 +323,18 @@ void ftrace_likely_update(struct ftrace_
#endif
#ifndef __compiletime_error
# define __compiletime_error(message)
-# define __compiletime_error_fallback(condition) \
+/*
+ * Sparse complains of variable sized arrays due to the temporary variable in
+ * __compiletime_assert. Unfortunately we can't just expand it out to make
+ * sparse see a constant array size without breaking compiletime_assert on old
+ * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
+ */
+# ifndef __CHECKER__
+# define __compiletime_error_fallback(condition) \
do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
-#else
+# endif
+#endif
+#ifndef __compiletime_error_fallback
# define __compiletime_error_fallback(condition) do { } while (0)
#endif
_
Patches currently in -mm which might be from james.hogan@xxxxxxxxxx are
compilerh-avoid-sparse-errors-in-__compiletime_error_fallback.patch
linux-next.patch
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