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Message-ID: <4cdd4ab9ddd16f1fb168266643264595782fd890.camel@perches.com>
Date: Tue, 14 Aug 2018 10:48:10 -0700
From: Joe Perches <joe@...ches.com>
To: Guenter Roeck <linux@...ck-us.net>, linux-kernel@...r.kernel.org
Cc: Rik van Riel <riel@...riel.com>, Mike Galbraith <efault@....de>,
Dave Hansen <dave.hansen@...el.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Build failures with gcc 4.5 and older
On Tue, 2018-08-14 at 10:09 -0700, Guenter Roeck wrote:
> Hi,
>
> Since commit c1a2f7f0c0645 ("mm: Allocate the mm_cpumask
> (mm->cpu_bitmap[]) dynamically based on nr_cpu_ids"), building
> the Linux kernel with gcc version 4.5 and older fails as follows.
>
> 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.
>
> Does that mean that gcc 4.5 and older are now officially no longer
> supported for compiling the kernel ?
>
> If so, would it make sense to update include/linux/compiler-gcc.h
> accordingly ?
And Documentation/process/changes.rst which shows a
minimum version required of gcc as 3.2, etc...
With cleaning up now unnecessary version tests in
compiler-gcc.h, something like:
---
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 573f5a7d42d4..020e4b9eee5c 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
@@ -148,47 +158,13 @@
#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
@@ -207,24 +183,19 @@
#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()
@@ -262,10 +233,6 @@
#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
@@ -274,8 +241,7 @@
*/
#define __visible __attribute__((externally_visible))
-#endif /* GCC_VERSION >= 40600 */
-
+/* gcc version specific checks */
#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
/*
@@ -309,10 +275,8 @@
* 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
@@ -341,10 +305,9 @@
* 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
@@ -353,16 +316,6 @@
#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.
@@ -375,12 +328,9 @@
#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)
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