compiler: Remove uninitialized_var() macro

Using uninitialized_var() is dangerous as it papers over real bugs[1] (or can in the future), and suppresses unrelated compiler warnings (e.g. "unused variable"). If the compiler thinks it is uninitialized, either simply initialize the variable or make compiler changes. As recommended[2] by[3] Linus[4], remove the macro. With the recent change to disable -Wmaybe-uninitialized in v5.7 in commit 78a5255 ("Stop the ad-hoc games with -Wno-maybe-initialized"), this is likely the best time to make this treewide change. [1] https://lore.kernel.org/lkml/[email protected]/ [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ Suggested-by: Linus Torvalds <[email protected]> Reviewed-by: Bart van Assche <[email protected]> Reviewed-by: Miguel Ojeda <[email protected]> Tested-by: Nathan Chancellor <[email protected]> Tested-by: Sedat Dilek <[email protected]> Signed-off-by: Kees Cook <[email protected]>
fracktal · Jul 16, 2020 · 63a0895 · 63a0895
1 parent 3f649ab
commit 63a0895
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diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
@@ -5,8 +5,6 @@
 
 /* Compiler specific definitions for Clang compiler */
 
-#define uninitialized_var(x) x = *(&(x))
-
 /* same as gcc, this was present in clang-2.6 so we can assume it works
  * with any version that can compile the kernel
  */

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
@@ -59,12 +59,6 @@
 	(typeof(ptr)) (__ptr + (off));					\
 })
 
-/*
- * A trick to suppress uninitialized variable warning without generating any
- * code
- */
-#define uninitialized_var(x) x = x
-
 #ifdef CONFIG_RETPOLINE
 #define __noretpoline __attribute__((__indirect_branch__("keep")))
 #endif

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
@@ -111,8 +111,6 @@
 # define noinline
 #endif
 
-#define uninitialized_var(x) x = *(&(x))
-
 #include <linux/types.h>
 
 /*

diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
@@ -110,8 +110,6 @@ static inline void free_page(unsigned long addr)
 	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
 	(type *)( (char *)__mptr - offsetof(type,member) );})
 
-#define uninitialized_var(x) x = x
-
 # ifndef likely
 #  define likely(x)	(__builtin_expect(!!(x), 1))
 # endif
-Original file line number
+Diff line change
@@ Expand Up / @@ -111,8 +111,6 @@ @@
     # define noinline
     #endif
-    #define uninitialized_var(x) x = *(&(x))
     #include <linux/types.h>
     /*
@@ Expand Down @@