[PATCH] Raise the minimum required gcc version to 4.6

From: Joe Perches
Date: Mon Aug 20 2018 - 16:15:59 EST

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Various architectures fail to build properly with older versions
of the gcc compiler.

An example from Guenter Roeck via this thread:
https://lore.kernel.org/lkml/20180814170904.GA12768@xxxxxxxxxxxx/

----------------------
In file included from ./include/linux/mm.h:17:0,
from ./include/linux/pid_namespace.h:7,
from ./include/linux/ptrace.h:10,
from arch/openrisc/kernel/asm-offsets.c:32:
./include/linux/mm_types.h:497:16: error: flexible array member in otherwise empty struct

This is just an example with gcc 4.5.1 for or32. I have seen the problem
with gcc 4.4 (for unicore32) as well.
----------------------

So update the minimum required version of gcc to 4.6.

Miscellanea:

o Update Documentation/process/changes.rst
o Remove and consolidate version test blocks in compiler-gcc.h
for versions lower than 4.6

Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
Documentation/process/changes.rst | 2 +-
include/linux/compiler-gcc.h | 86 ++++++++-------------------------------
2 files changed, 19 insertions(+), 69 deletions(-)

diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 7a92a06f90de..61f918b10a0c 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -29,7 +29,7 @@ you probably needn't concern yourself with isdn4k-utils.
====================== =============== ========================================
Program Minimal version Command to check the version
====================== =============== ========================================
-GNU C 3.2 gcc --version
+GNU C 4.6 gcc --version
GNU make 3.81 make --version
binutils 2.20 ld -v
flex 2.5.35 flex --version
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 3e70b7d4e9ed..250b9b7cfd60 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -10,6 +10,10 @@
+ __GNUC_MINOR__ * 100 \
+ __GNUC_PATCHLEVEL__)

+#if GCC_VERSION < 40600
+# error Sorry, your compiler is too old - please upgrade it.
+#endif
+
/* Optimization barrier */

/* The "volatile" is due to gcc bugs */
@@ -58,6 +62,12 @@
#define OPTIMIZER_HIDE_VAR(var) \
__asm__ ("" : "=r" (var) : "0" (var))

+/*
+ * A trick to suppress uninitialized variable warning without generating any
+ * code
+ */
+#define uninitialized_var(x) x = x
+
#ifdef __CHECKER__
#define __must_be_array(a) 0
#else
@@ -91,7 +101,7 @@
* A lot of inline functions can cause havoc with function tracing.
*/
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
- !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
+ !defined(CONFIG_OPTIMIZE_INLINING)
#define inline \
inline __attribute__((always_inline, unused)) notrace __gnu_inline
#else
@@ -147,47 +157,13 @@
#define __always_unused __attribute__((unused))
#define __mode(x) __attribute__((mode(x)))

-/* gcc version specific checks */
-
-#if GCC_VERSION < 30200
-# error Sorry, your compiler is too old - please upgrade it.
-#endif
-
-#if GCC_VERSION < 30300
-# define __used __attribute__((__unused__))
-#else
-# define __used __attribute__((__used__))
-#endif
-
-#ifdef CONFIG_GCOV_KERNEL
-# if GCC_VERSION < 30400
-# error "GCOV profiling support for gcc versions below 3.4 not included"
-# endif /* __GNUC_MINOR__ */
-#endif /* CONFIG_GCOV_KERNEL */
-
-#if GCC_VERSION >= 30400
#define __must_check __attribute__((warn_unused_result))
#define __malloc __attribute__((__malloc__))
-#endif
-
-#if GCC_VERSION >= 40000
-
-/* GCC 4.1.[01] miscompiles __weak */
-#ifdef __KERNEL__
-# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
-# error Your version of gcc miscompiles the __weak directive
-# endif
-#endif

#define __used __attribute__((__used__))
#define __compiler_offsetof(a, b) \
__builtin_offsetof(a, b)

-#if GCC_VERSION >= 40100
-# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
-#endif
-
-#if GCC_VERSION >= 40300
/* 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
@@ -206,24 +182,19 @@

#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__ */
-#endif /* GCC_VERSION >= 40300 */
-
-#if GCC_VERSION >= 40400
#define __optimize(level) __attribute__((__optimize__(level)))
#define __nostackprotector __optimize("no-stack-protector")
-#endif /* GCC_VERSION >= 40400 */

-#if GCC_VERSION >= 40500
+#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)

#ifndef __CHECKER__
+#define __compiletime_warning(message) __attribute__((warning(message)))
+#define __compiletime_error(message) __attribute__((error(message)))
+
#ifdef LATENT_ENTROPY_PLUGIN
#define __latent_entropy __attribute__((latent_entropy))
#endif
-#endif
+#endif /* __CHECKER__ */

/*
* calling noreturn functions, __builtin_unreachable() and __builtin_trap()
@@ -261,10 +232,6 @@
#define randomized_struct_fields_end } __randomize_layout;
#endif

-#endif /* GCC_VERSION >= 40500 */
-
-#if GCC_VERSION >= 40600
-
/*
* When used with Link Time Optimization, gcc can optimize away C functions or
* variables which are referenced only from assembly code. __visible tells the
@@ -273,8 +240,7 @@
*/
#define __visible __attribute__((externally_visible))

-#endif /* GCC_VERSION >= 40600 */
-
+/* gcc version specific checks */

#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
/*
@@ -308,10 +274,8 @@
* folding in __builtin_bswap*() (yet), so don't set these for it.
*/
#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
-#if GCC_VERSION >= 40400
#define __HAVE_BUILTIN_BSWAP32__
#define __HAVE_BUILTIN_BSWAP64__
-#endif
#if GCC_VERSION >= 40800
#define __HAVE_BUILTIN_BSWAP16__
#endif
@@ -340,10 +304,9 @@
* https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
*/
#define __designated_init __attribute__((designated_init))
+#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
#endif

-#endif /* gcc version >= 40000 specific checks */
-
#if !defined(__noclone)
#define __noclone /* not needed */
#endif
@@ -352,16 +315,6 @@
#define __no_sanitize_address
#endif

-/*
- * A trick to suppress uninitialized variable warning without generating any
- * code
- */
-#define uninitialized_var(x) x = x
-
-#if GCC_VERSION >= 50100
-#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
-#endif
-
/*
* Turn individual warnings and errors on and off locally, depending
* on version.
@@ -374,12 +327,9 @@
#define __diag_GCC_warn warning
#define __diag_GCC_error error

-/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */
-#if GCC_VERSION >= 40600
#define __diag_str1(s) #s
#define __diag_str(s) __diag_str1(s)
#define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
-#endif

#if GCC_VERSION >= 80000
#define __diag_GCC_8(s) __diag(s)
--
2.15.0

Next message: Tony Krowiak: "Re: [PATCH v9 22/22] s390: doc: detailed specifications for AP virtualization"
Previous message: Michal Wnukowski: "Re: [PATCH v2] Bugfix for handling of shadow doorbell buffer."
Next in thread: Nick Desaulniers: "Re: [PATCH] Raise the minimum required gcc version to 4.6"
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