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SubjectRe: 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@xenotime.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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