linux-kernel - [PATCH 4/7] Compiler Attributes: homogenize __must_be

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Date:   Fri, 31 Aug 2018 19:05:11 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Eli Friedman <efriedma@...eaurora.org>,
        Christopher Li <sparse@...isli.org>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Joe Perches <joe@...ches.com>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 4/7] Compiler Attributes: homogenize __must_be_array

Different definitions of __must_be_array:

  * gcc: disabled for __CHECKER__

  * clang: same definition as gcc's, but without __CHECKER__

  * intel: the comment claims __builtin_types_compatible_p()
    is unsupported; but icc seems to support it since 13.0.1
    (released in 2012). See https://godbolt.org/z/S0l6QQ

Therefore, we can remove all of them and have a single definition
in compiler.h

Cc: Eli Friedman <efriedma@...eaurora.org>
Cc: Christopher Li <sparse@...isli.org>
Cc: Kees Cook <keescook@...omium.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Dominique Martinet <asmadeus@...ewreck.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
---
 include/linux/compiler-clang.h | 1 -
 include/linux/compiler-gcc.h   | 7 -------
 include/linux/compiler-intel.h | 3 ---
 include/linux/compiler.h       | 7 +++++++
 4 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index efda74f4eeba..0aee694d3ab8 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -41,6 +41,5 @@
  * compilers, like ICC.
  */
 #define barrier() __asm__ __volatile__("" : : : "memory")
-#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
 #define __assume_aligned(a, ...)	\
 	__attribute__((assume_aligned(a, ## __VA_ARGS__)))
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index dbfbecf703f8..66e1eb8822d9 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -68,13 +68,6 @@
  */
 #define uninitialized_var(x) x = x
 
-#ifdef __CHECKER__
-#define __must_be_array(a)	0
-#else
-/* &a[0] degrades to a pointer: a different type from an array */
-#define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
-#endif
-
 #ifdef RETPOLINE
 #define __noretpoline __attribute__((indirect_branch("keep")))
 #endif
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index 4c7f9befa9f6..18bd4362deaa 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -29,9 +29,6 @@
  */
 #define OPTIMIZER_HIDE_VAR(var) barrier()
 
-/* Intel ECC compiler doesn't support __builtin_types_compatible_p() */
-#define __must_be_array(a) 0
-
 #endif
 
 /* icc has this, but it's called _bswap16 */
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index e0e55eb3f242..e4a702f99e50 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -357,4 +357,11 @@ static inline void *offset_to_ptr(const int *off)
 	compiletime_assert(__native_word(t),				\
 		"Need native word sized stores/loads for atomicity.")
 
+#ifdef __CHECKER__
+#define __must_be_array(a)	0
+#else
+/* &a[0] degrades to a pointer: a different type from an array */
+#define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
+#endif
+
 #endif /* __LINUX_COMPILER_H */
-- 
2.17.1