linux-kernel - [patch] compiler, clang: move inline definition to compiler-gcc.h

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Message-ID: <alpine.DEB.2.10.1706062252500.124004@chino.kir.corp.google.com>
Date:   Tue, 6 Jun 2017 22:56:49 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Matthias Kaehlcke <mka@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Steven Rostedt <rostedt@...dmis.org>,
        Douglas Anderson <dianders@...omium.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Mark Brown <broonie@...nel.org>,
        David Miller <davem@...emloft.net>
Subject: [patch] compiler, clang: move inline definition to compiler-gcc.h

The motivation of commit abb2ea7dfd82 ("compiler, clang: suppress warning 
for unused static inline functions") is to suppress clang's warnings about 
unused static inline functions.

Clang defines __GNUC__ so it inherits all of compiler-gcc.h as well, so 
the redefinition of `inline' ends up overriding the definition in 
compiler-gcc.h.

Simply annotate all inline functions as __attribute__((unused)).  It's 
necessary to suppress the warning for clang and is implicit with gcc.

Reported-by: Matthias Kaehlcke <mka@...omium.org>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 Matthias, please add your Tested-by if this works for you, thanks!

 include/linux/compiler-clang.h |  7 -------
 include/linux/compiler-gcc.h   | 18 ++++++++++--------
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -15,10 +15,3 @@
  * with any version that can compile the kernel
  */
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
-
-/*
- * GCC does not warn about unused static inline functions for
- * -Wunused-function.  This turns out to avoid the need for complex #ifdef
- * directives.  Suppress the warning in clang as well.
- */
-#define inline inline __attribute__((unused))
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 0efef9cf014f..1264f0688b10 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -65,19 +65,21 @@
 #endif
 
 /*
- * Force always-inline if the user requests it so via the .config,
- * or if gcc is too old:
+ * Force always_inline if the user requests it via the .config, or if gcc is
+ * version 3 or earlier.  Also disable unused static inline function warnings
+ * to avoid the need for complex #ifdef directives: this is implicit with gcc
+ * but is needed for clang, which also sets __GNUC__.
  */
 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
     !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
-#define inline		inline		__attribute__((always_inline)) notrace
-#define __inline__	__inline__	__attribute__((always_inline)) notrace
-#define __inline	__inline	__attribute__((always_inline)) notrace
+#define inline		inline		__attribute__((always_inline,unused)) notrace
+#define __inline__	__inline__	__attribute__((always_inline,unused)) notrace
+#define __inline	__inline	__attribute__((always_inline,unused)) notrace
 #else
 /* A lot of inline functions can cause havoc with function tracing */
-#define inline		inline		notrace
-#define __inline__	__inline__	notrace
-#define __inline	__inline	notrace
+#define inline		inline		__attribute__((unused)) notrace
+#define __inline__	__inline__	__attribute__((unused)) notrace
+#define __inline	__inline	__attribute__((unused)) notrace
 #endif
 
 #define __always_inline	inline __attribute__((always_inline))