linux-kernel - [PATCH] compiler: add support for gcc 6

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Message-ID: <20150415073259.72ddfc9c@kryten>
Date:	Wed, 15 Apr 2015 07:32:59 +1000
From:	Anton Blanchard <anton@...ba.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Modra <amodra@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] compiler: add support for gcc 6

gcc has recently bumped its major version and this is causing kernel
build errors. Create include/linux/compiler-gcc6.h which is a copy
of compiler-gcc5.h, minus a few comments that no longer apply.

Signed-off-by: Anton Blanchard <anton@...ba.org>
---

I'm told the versioning scheme in gcc has changed, and to expect
much more rev'ing of the major version. We should probably rethink
if we need a separate file per major version.

diff --git a/include/linux/compiler-gcc6.h b/include/linux/compiler-gcc6.h
new file mode 100644
index 0000000..ba064fa
--- /dev/null
+++ b/include/linux/compiler-gcc6.h
@@ -0,0 +1,59 @@
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc6.h> directly, include <linux/compiler.h> instead."
+#endif
+
+#define __used				__attribute__((__used__))
+#define __must_check			__attribute__((warn_unused_result))
+#define __compiler_offsetof(a, b)	__builtin_offsetof(a, b)
+
+/* Mark functions as cold. gcc will assume any path leading to a call
+   to them will be unlikely.  This means a lot of manual unlikely()s
+   are unnecessary now for any paths leading to the usual suspects
+   like BUG(), printk(), panic() etc. [but let's keep them for now for
+   older compilers]
+
+   gcc also has a __attribute__((__hot__)) to move hot functions into
+   a special section, but I don't see any sense in this right now in
+   the kernel context */
+#define __cold			__attribute__((__cold__))
+
+#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#ifndef __CHECKER__
+# define __compiletime_warning(message) __attribute__((warning(message)))
+# define __compiletime_error(message) __attribute__((error(message)))
+#endif /* __CHECKER__ */
+
+/*
+ * Mark a position in code as unreachable.  This can be used to
+ * suppress control flow warnings after asm blocks that transfer
+ * control elsewhere.
+ */
+#define unreachable() __builtin_unreachable()
+
+/* Mark a function definition as prohibited from being cloned. */
+#define __noclone	__attribute__((__noclone__))
+
+/*
+ * Tell the optimizer that something else uses this function or variable.
+ */
+#define __visible __attribute__((externally_visible))
+
+/*
+ * GCC 'asm goto' miscompiles certain code sequences:
+ *
+ *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
+ *
+ * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
+ *
+ * (asm goto is automatically volatile - the naming reflects this.)
+ */
+#define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)
+
+#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
+#define __HAVE_BUILTIN_BSWAP32__
+#define __HAVE_BUILTIN_BSWAP64__
+#define __HAVE_BUILTIN_BSWAP16__
+#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
+
+#define KASAN_ABI_VERSION 4
-- 
2.1.0

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