From 9490991482a2091a828d997adbc088e24c310a4d Mon Sep 17 00:00:00 2001 From: Borislav Petkov 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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) :