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Date:   Mon, 28 May 2018 10:07:26 -0500
From:   Segher Boessenkool <segher@kernel.crashing.org>
To:     Christophe Leroy <christophe.leroy@c-s.fr>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/Makefile: fix build failure by disabling attribute-alias warning
Message-ID: <20180528150726.GC17342@gate.crashing.org>
References: <0adce33cf1c70ac7203f8ebd987a912451aabd45.1527517001.git.christophe.leroy@c-s.fr> <e81f81b7-2bf5-7f9a-919f-87972bf1a9db@c-s.fr>
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On Mon, May 28, 2018 at 02:39:37PM +0000, Christophe Leroy wrote:
> 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]

So yes, these are actually different (int vs. long).

> 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]

And this one is quite spectacularly different.


Try putting this before the wacko aliases:

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wattribute-alias"

and this after:

#pragma GCC diagnostic pop

so that you will get this quite useful warning for all other code.


Segher