gcc 4.9 build warnings (was: Re: next build: 2674 warnings 1 failures (next/next-20141022))

[Olof Johansson]

On Fri, Oct 24, 2014 at 2:56 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Fri, Oct 24, 2014 at 02:47:29PM -0700, Olof Johansson wrote:
>> On Thu, Oct 23, 2014 at 3:26 PM, Russell King - ARM Linux
>> <linux at arm.linux.org.uk> wrote:
>> > On Thu, Oct 23, 2014 at 10:31:07PM +0200, Arnd Bergmann wrote:
>> >> On Thursday 23 October 2014 17:12:20 Russell King - ARM Linux wrote:
>> >> >
>> >> > > I haven't found the code in gcc that performs the type check for
>> >> > > printf, but I've found a comment about that code intentionally
>> >> > > resolving the type (printing 'unsigned int') when the typedef
>> >> > > does not match the expected type.
>> >> >
>> >> > If I had a copy of the GCC 4.9 source locally, I'd dig into it too and
>> >> > try to work out what's going on.  My gut feeling is that it's a bug in
>> >> > GCC rather than something which the kernel is doing wrong.
>> >> >
>> >>
>> >> I suspect it has something to do with the way that Olof's gcc is built,
>> >> since it doesn't happen for me using the same kernel source and gcc-4.9.1
>> >> or 4.10-prerelease.
>> >>
>> >> The fact that it doesn't define __linux__ means that it must be configured
>> >> in some other way than what I do or what I get from the distros.
>> >
>> > Hmm, which may mean that it does expect "unsigned long" for size_t.
>> >
>> > Olof, please can you try this fragment:
>> >
>> > typedef __SIZE_TYPE__ gcc_size_t;
>> > #include <stdio.h>
>> > int main() { size_t size = 1; printf("%zu\n", size); return 0; }
>> >
>> > with "arm-linux-gcc -E -o - test.c | grep size_t" and check what the
>> > actual typedefs passed to the compiler proper are?  Thanks.
>>
>>
>> Since it's a baremetal compiler, there's no stdio.h. Anyway, taking
>> out the include line:
>>
>> typedef unsigned int gcc_size_t;
>> int main() { size_t size = 1; printf("%zu\n", size); return 0; }
>>
>>
>> I guess I should just look at building a full compiler set instead of
>> this silliness. On the other hand, it's good to get it exposed I
>> suppose.
>
> In which case, use #include <stddef.h> which should be provided by
> the compiler.

Yes, of course. Changing stdio to stddef:

$ /usr/local/cross-4.9.1/bin/arm-linux-eabi-gcc -E -o - test.c | grep size_t
typedef unsigned int gcc_size_t;
typedef unsigned int size_t;
int main() { size_t size = 1; printf("%zu\n", size); return 0; }


-Olof