linux-kernel - Re: Build regressions/improvements in v3.3-rc5 (C lang questions)

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Date:	Tue, 28 Feb 2012 16:24:42 -0800
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: Build regressions/improvements in v3.3-rc5 (C lang questions)

On 02/28/2012 04:08 PM, Linus Torvalds wrote:

> On Tue, Feb 28, 2012 at 3:41 PM, Randy Dunlap <rdunlap@...otime.net> wrote:
>>
>>>   + src/drivers/usb/misc/sisusbvga/sisusb.c: warning: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t':  => 982
>>>   + src/fs/ecryptfs/miscdev.c: warning: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t':  => 448, 488
>>
>> Do the (2) above mean that some platform's gcc is borked?
>> (I don't see these on i386 or x86_64.)
> 
> Hmm. We had something similar long ago on i386, where the kernel
> "size_t" was "unsigned long", but user-mode size_t was "unsigned int"
> (or maybe it was the other way around). Anyway, it's obviously
> physically the same type, but it would make gcc unhappy because gcc
> felt that somebody was doing something bad.
> 
>>>   + src/fs/ecryptfs/miscdev.c: warning: format '%lu' expects type 'long unsigned int', but argument 4 has type 'unsigned int':  => 433, 433:60
>>
>> I can see that warning on 32-bit i386 (X86_32), but if I change the
>> "%lu" to "%u", it causes this warning on 64-bit x86_64:
>>
>> fs/ecryptfs/miscdev.c:433:38: warning: format '%u' expects type 'unsigned int', but argument 4 has type 'long unsigned int'
>>
>> so how is this supposed to be handled?
> 
> I suspect that one should be "%zu", because we have
> 
>   /* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
>   #define MAX_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
>                                  + ECRYPTFS_MAX_PKT_LEN_SIZE \
>                                  + sizeof(struct ecryptfs_message) \
>                                  + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
> 
> so it's the "sizeof(struct ecryptfs_message)" that makes it a size_t
> (everything else is int, if I look at it right, and int+size_t is
> going to be size_t)
> 
> Of course, if the platform then has the compiler and the kernel
> disagreeing about size_t like above, that isn't going to help
> anything. But does it fix the x86-32/64 warnings?


Yes, it does fix both cases (and I should have tried that).
Thanks.

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