From: Christophe Leroy > Sent: 17 March 2021 17:35 > > Le 17/03/2021 à 13:51, David Laight a écrit : > > From: Christophe Leroy > >> Sent: 16 March 2021 15:41 > > ... > >>>> include/linux/types.h:typedef __kernel_ptrdiff_t ptrdiff_t; > >>>> > >>>> And get: > >>>> > >>>> CC mm/kfence/report.o > >>>> In file included from ./include/linux/printk.h:7, > >>>> from ./include/linux/kernel.h:16, > >>>> from mm/kfence/report.c:10: > >>>> mm/kfence/report.c: In function 'kfence_report_error': > >>>> ./include/linux/kern_levels.h:5:18: warning: format '%td' expects argument > >>>> of type 'ptrdiff_t', but argument 6 has type 'long int' [-Wformat=] > >>> > >>> This is declared as > >>> const ptrdiff_t object_index = meta ? meta - kfence_metadata : -1; > >>> so maybe something with that goes wrong? What happens if you delete the > >>> (useless) "const" here? > > > > The obvious thing to try is changing it to 'int'. > > That will break 64bit builds, but if it fixes the 32bit one > > it will tell you what type gcc is expecting. > > > > Yes, if defining 'object_index' as int, gcc is happy. > If removing the powerpc re-definition of ptrdiff_t typedef in > https://elixir.bootlin.com/linux/v5.12-rc3/source/arch/powerpc/include/uapi/asm/posix_types.h , it > works great as well. > > So seems like gcc doesn't take into account the typedef behind ptrdiff_t, it just expects it to be > int on 32 bits ? gcc never cares how ptrdiff_t (or any of the related types) is defined it requires int or long for the format depending on the architecture. The error message will say ptrdiff_t or size_t (etc) - but that is just in the error message. So the ppc32 uapi definition of __kernel_ptrdiff_t is wrong. However it is probably set in stone. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
