Hi Yamada-san, On Mon, Dec 15, 2014 at 11:51 AM, Masahiro Yamada <yamad...@jp.panasonic.com> wrote: > Geert Uytterhoeven <ge...@linux-m68k.org> wrote: >> On Mon, Dec 15, 2014 at 10:32 AM, Masahiro Yamada >> <yamad...@jp.panasonic.com> wrote: >> > I read through Documentation/printk-formats.txt >> > >> > It clearly says to use "%zu" or "%zx" to print size_t variables, >> > but I still have a question. >> > >> > >> > Assume we have code something like: >> > >> > printk("%zx", (size_t)10); >> > >> > >> > I think this code works fine as long as it includes >> > the compiler-provided <stddef.h>. >> > >> > In the kernel space, however, <stddef.h> is never included. >> > Instead, size_t is defined by include/linux/types.h >> > and include/uapi/asm-generic/posix_types.h. >> > >> > >> > That is, size_t is defined independently from the compiler you are using, >> > although the compiler still decides which variable type is expected for >> > the "%zx" format. >> >> That's correct. >> >> > This causes compiler warnings for some compilers. >> > >> > On bare-metal m68k toolchains, for example, size_t is "unsignd long", >> > whearas it is "unsigned int" on kernel.org m68k toolchains. >> > >> > >> > I see such warnings when I built the kernel with bare-metal m68k >> > toolchains. >> > >> > >> > $ git describe >> > v3.18 >> > $ make ARCH=m68k CROSS_COMPILE=m68k-elf- defconfig all >> > HOSTCC scripts/basic/fixdep >> > HOSTCC scripts/kconfig/conf.o >> > SHIPPED scripts/kconfig/zconf.tab.c >> > SHIPPED scripts/kconfig/zconf.lex.c >> > SHIPPED scripts/kconfig/zconf.hash.c >> > HOSTCC scripts/kconfig/zconf.tab.o >> > HOSTLD scripts/kconfig/conf >> > *** Default configuration is based on 'multi_defconfig' >> > kernel/time/Kconfig:163:warning: range is invalid >> > # >> > # configuration written to .config >> > # >> > >> > [ snip ] >> > >> > LD init/mounts.o >> > CC init/initramfs.o >> > init/initramfs.c: In function 'populate_rootfs': >> > init/initramfs.c:635:5: warning: format '%zd' expects argument of type >> > 'signed size_t', but argument 2 has type 'ssize_t' [-Wformat] >> >> Please use a compiler configured for Linux, i.e. m68k-linux-*. > > > Yes, I can use it, but I am still curious. > > Do we have a good reason to keep this limitation? > > (All the problem I could see for using GCC that was not configured for Linux > was just the printk-related warnings.) > > > Instead of hard-coding the size_t type, > can we use compiler-provided __SIZE_TYPE__ (or include <stddef.h>) ??
Note that cris and s390 used __SIZE_TYPE__ in kernel headers before, but it caused other compiler warnings due to a mismatch in the base types for size_t and ssize_t, cfr. https://lkml.org/lkml/2012/8/12/36. AFAIK, there's no __SSIZE_TYPE__. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/