From 9490991482a2091a828d997adbc088e24c310a4d Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bbpetkov@yahoo.de>
Date: Sun, 6 May 2007 14:49:17 -0700
Subject: [PATCH] Add unitialized_var() macro for suppressing gcc warnings
Introduce a macro for suppressing gcc from generating a warning about a
probable uninitialized state of a variable.
Example:
- spinlock_t *ptl;
+ spinlock_t *uninitialized_var(ptl);
Not a happy solution, but those warnings are obnoxious.
- Using the usual pointlessly-set-it-to-zero approach wastes several
bytes of text.
- Using a macro means we can (hopefully) do something else if gcc changes
cause the `x = x' hack to stop working
- Using a macro means that people who are worried about hiding true bugs
can easily turn it off.
Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/compiler-gcc3.h | 6 ++++++
include/linux/compiler-gcc4.h | 6 ++++++
include/linux/compiler-intel.h | 2 ++
mm/memory.c | 2 +-
4 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h
index 1698b845761f..ecd621fd27d2 100644
--- a/include/linux/compiler-gcc3.h
+++ b/include/linux/compiler-gcc3.h
@@ -13,4 +13,10 @@
#define __must_check __attribute__((warn_unused_result))
#endif
+/*
+ * A trick to suppress uninitialized variable warning without generating any
+ * code
+ */
+#define uninitialized_var(x) x = x
+
#define __always_inline inline __attribute__((always_inline))
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index 6f5cc6f0e7a6..fd0cc7c4a636 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -16,3 +16,9 @@
#define __must_check __attribute__((warn_unused_result))
#define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
#define __always_inline inline __attribute__((always_inline))
+
+/*
+ * A trick to suppress uninitialized variable warning without generating any
+ * code
+ */
+#define uninitialized_var(x) x = x
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index 1d1c3ceaff4e..a436eea43912 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -22,3 +22,5 @@
(typeof(ptr)) (__ptr + (off)); })
#endif
+
+#define uninitialized_var(x) x
diff --git a/mm/memory.c b/mm/memory.c
index c252aae544e9..1d647ab0ee72 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1455,7 +1455,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
pte_t *pte;
int err;
struct page *pmd_page;
- spinlock_t *ptl = ptl; /* Suppress gcc warning */
+ spinlock_t *uninitialized_var(ptl);
pte = (mm == &init_mm) ?
pte_alloc_kernel(pmd, addr) :