Messages in this thread |  | | Date | Mon, 15 Dec 2014 18:32:18 +0900 | From | Masahiro Yamada <> | Subject | [Question] How to print size_t type variable? |
| |
Hi experts,
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.
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]
Any advice? How to fix this issue?
Best Regards Masahiro Yamada
|  |