On Mon, Feb 27, 2017 at 12:38:16PM +0300, Alexey Dobriyan wrote: > On Sat, Feb 25, 2017 at 1:35 AM, Dmitry V. Levin <l...@altlinux.org> wrote: > > On Fri, Feb 24, 2017 at 05:35:33PM +0300, Alexey Dobriyan wrote: > >> On Thu, Feb 23, 2017 at 02:44:31PM -0800, a...@linux-foundation.org wrote: > >> > /usr/include/linux/sysctl.h:38:2: error: unknown type name 'size_t' > >> > size_t *oldlenp; > >> > /usr/include/linux/sysctl.h:40:2: error: unknown type name 'size_t' > >> > size_t newlen; > >> > >> > --- > >> > a/include/uapi/linux/sysctl.h~uapi-fix-linux-sysctlh-userspace-compilation-errors > >> > +++ a/include/uapi/linux/sysctl.h > >> > @@ -26,6 +26,10 @@ > >> > #include <linux/types.h> > >> > #include <linux/compiler.h> > >> > > >> > +#ifndef __KERNEL__ > >> > +#include <stddef.h> /* For size_t. */ > >> > +#endif > >> > >> There is __kernel_size_t for cases like this. > > > > No, __kernel_size_t is not for cases like this because size_t differs > > from __kernel_size_t on x32 and mips n32. > > > > Fortunately, there is no sysctl syscall entry on x32, but on mips m32 > > it is there with number 6152, implemented using compat_sys_sysctl. > > The latter operates with argument of type struct compat_sysctl_args* > > where newlen is of type compat_size_t. > > > > If you change it from size_t to __kernel_size_t, you'll break mips n32. > > You're gluing kernel interface to an userspace header > which kernel doesn't control.
Are you sure it's me who does the gluing? As no uapi header provides a definition of size_t, they are essentially relying on size_t being provided elsewhere. For this reason, inclusion of <stddef.h> is the most conservative fix. > How can this fix anything? For example, AC_CHECK_HEADERS([<linux/sysctl.h>]) doesn't work, one has to use AC_CHECK_HEADERS([<linux/sysctl.h>], , , [#include <stddef.h>]) instead. The same issue arises with other autoconf checks. I think that every uapi header file should be standalone, i.e. it must include, directly or indirectly, every definition it uses, so that no user should have to guess header dependencies. -- ldv
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