linux-kernel - Re: [PATCH] powerpc/Makefile: fix build failure by disabling attribute-alias warning

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Date:   Mon, 28 May 2018 14:39:37 +0000
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        segher@...nel.crashing.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/Makefile: fix build failure by disabling
 attribute-alias warning



On 05/28/2018 02:17 PM, Christophe Leroy wrote:
> Latest GCC version emit many warnings similar to the following one.

Oops, forgot to include the failure text:

In file included from arch/powerpc/kernel/syscalls.c:24:
./include/linux/syscalls.h:233:18: warning: 'sys_mmap2' alias between 
functions of incompatible types 'long int(long unsigned int,  size_t, 
long unsigned int,  long unsigned int,  long unsigned int,  long 
unsigned int)' {aka 'long int(long unsigned int,  unsigned int,  long 
unsigned int,  long unsigned int,  long unsigned int,  long unsigned 
int)'} and 'long int(long int,  long int,  long int,  long int,  long 
int,  long int)' [-Wattribute-alias]
   asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
                   ^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro 
'SYSCALL_DEFINE6'
  SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
  ^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
   asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
                   ^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro 
'SYSCALL_DEFINE6'
  SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
  ^~~~~~~~~~~~~~~
./include/linux/syscalls.h:233:18: warning: 'sys_mmap' alias between 
functions of incompatible types 'long int(long unsigned int,  size_t, 
long unsigned int,  long unsigned int,  long unsigned int,  off_t)' {aka 
'long int(long unsigned int,  unsigned int,  long unsigned int,  long 
unsigned int,  long unsigned int,  long int)'} and 'long int(long int, 
long int,  long int,  long int,  long int,  long int)' [-Wattribute-alias]
   asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
                   ^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:72:1: note: in expansion of macro 
'SYSCALL_DEFINE6'
  SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
  ^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
   asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
                   ^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:72:1: note: in expansion of macro 
'SYSCALL_DEFINE6'
  SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
  ^~~~~~~~~~~~~~~
   CC      arch/powerpc/kernel/irq.o
   CC      arch/powerpc/kernel/align.o
   CC      arch/powerpc/kernel/signal_32.o
In file included from arch/powerpc/kernel/signal_32.c:29:
./include/linux/syscalls.h:233:18: warning: 'sys_swapcontext' alias 
between functions of incompatible types 'long int(struct ucontext *, 
struct ucontext *, long int)' and 'long int(long int,  long int,  long 
int)' [-Wattribute-alias]
   asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
                   ^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1044:1: note: in expansion of macro 
'SYSCALL_DEFINE3'
  SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
  ^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
   asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
                   ^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1044:1: note: in expansion of macro 
'SYSCALL_DEFINE3'
  SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
  ^~~~~~~~~~~~~~~
./include/linux/syscalls.h:233:18: warning: 'sys_debug_setcontext' alias 
between functions of incompatible types 'long int(struct ucontext *, 
int,  struct sig_dbg_op *)' and 'long int(long int,  long int,  long 
int)' [-Wattribute-alias]
   asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
                   ^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1232:1: note: in expansion of macro 
'SYSCALL_DEFINE3'
  SYSCALL_DEFINE3(debug_setcontext, struct ucontext __user *, ctx,
  ^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
   asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
                   ^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro 
'__SYSCALL_DEFINEx'
   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:213:36: note: in expansion of macro 
'SYSCALL_DEFINEx'
  #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, 
__VA_ARGS__)
                                     ^~~~~~~~~~~~~~~
arch/powerpc/kernel/signal_32.c:1232:1: note: in expansion of macro 
'SYSCALL_DEFINE3'
  SYSCALL_DEFINE3(debug_setcontext, struct ucontext __user *, ctx,
  ^~~~~~~~~~~~~~~


Christophe

> 
> As arch/powerpc code is built with -Werror, this breaks build with
> GCC 8.1
> 
> This patch inhibits that warning
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>   arch/powerpc/Makefile | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index 26ccd0b91512..d6c557530ce8 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -145,6 +145,8 @@ CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mno-pointers-to-nested-functions)
>   CFLAGS-$(CONFIG_PPC32)	:= -ffixed-r2 $(MULTIPLEWORD)
>   CFLAGS-$(CONFIG_PPC32)	+= $(call cc-option,-mno-readonly-in-sdata)
>   
> +CFLAGS-y += $(call cc-option,-Wno-attribute-alias)
> +
>   ifeq ($(CONFIG_PPC_BOOK3S_64),y)
>   ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y)
>   CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=power8
>