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>

diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h
index 1698b845761f0127b640135e783b5f7ed0758a62..ecd621fd27d2415376ea1d123b353edfd2ee7843 100644 (file)
--- 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 6f5cc6f0e7a66ca521fb1978f27a51099666ec3d..fd0cc7c4a636e77dbf5a502b31b85f760cb088e9 100644 (file)
--- 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 1d1c3ceaff4ed62b6b2e971a0ca7588f969c8431..a436eea439120fb63df3ecb46fe220a2b88e5e23 100644 (file)
--- 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 c252aae544e9341925bed2cb49ec7b0e3bc7e9d3..1d647ab0ee72d02f8ad735273d46b862b3fbcee9 100644 (file)
--- 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) :