Hi Tom, Simon, other developers,
Since commit 0d296cc2d3b8 (Provide option to avoid defining a custom version of uintptr_t) and commit 4166ecb247a1 (Add some standard headers external code might need), I have been wondering if they were right decisions.
As arch/arm/include/asm/types.h of Linux Kernel says, using 'stdint.h' is not feasible.
-------------------------------------->8------------------------------------- /* * The C99 types uintXX_t that are usually defined in 'stdint.h' are not as * unambiguous on ARM as you would expect. For the types below, there is a * difference on ARM between GCC built for bare metal ARM, GCC built for glibc * and the kernel itself, which results in build errors if you try to build with * -ffreestanding and include 'stdint.h' (such as when you include 'arm_neon.h' * in order to use NEON intrinsics) * * As the typedefs for these types in 'stdint.h' are based on builtin defines * supplied by GCC, we can tweak these to align with the kernel's idea of those * types, so 'linux/types.h' and 'stdint.h' can be safely included from the same * source file (provided that -ffreestanding is used). * * int32_t uint32_t uintptr_t * bare metal GCC long unsigned long unsigned int * glibc GCC int unsigned int unsigned int * kernel int unsigned int unsigned long */ --------------------------------------8<----------------------------------------
Actually, the kernel never includes <stdint.h> except host programs.
Commit 0d296cc2d3b8 introduced "USE_STDINT", but it causes type conflicts depending on which GCC is used.
With ARM bare metal GCC,
yamada@beagle:~/workspace/u-boot$ make omap3_beagle_defconfig all CROSS_COMPILE=arm-none-eabi- USE_STDINT=1 # # configuration written to .config # # # configuration written to spl/.config # scripts/kconfig/conf --silentoldconfig Kconfig scripts/kconfig/conf --silentoldconfig Kconfig CHK include/config.h GEN include/autoconf.mk GEN include/autoconf.mk.dep GEN spl/include/autoconf.mk CHK include/config/uboot.release CHK include/generated/version_autogenerated.h CHK include/generated/timestamp_autogenerated.h UPD include/generated/timestamp_autogenerated.h CC lib/asm-offsets.s In file included from /opt/arm-2011.03/bin/../lib/gcc/arm-none-eabi/4.5.2/include/stdint.h:5:0, from include/compiler.h:117, from include/image.h:19, from include/common.h:85, from lib/asm-offsets.c:15: /opt/arm-2011.03/bin/../lib/gcc/arm-none-eabi/4.5.2/include/stdint-gcc.h:40:24: error: conflicting types for 'int32_t' include/linux/types.h:99:17: note: previous declaration of 'int32_t' was here /opt/arm-2011.03/bin/../lib/gcc/arm-none-eabi/4.5.2/include/stdint-gcc.h:52:25: error: conflicting types for 'uint32_t' include/linux/types.h:105:17: note: previous declaration of 'uint32_t' was here make[2]: *** [lib/asm-offsets.s] Error 1 make[1]: *** [prepare0] Error 2 make: *** [__build_one_by_one] Error 2
OK, we can fix "int32_t" and "uint32_t", but it still seems strange to see that "uint32_t" is defined as "unsigned long", whereas "u32" is defined as "unsigned int".
If so, must we fix "u32", "s32", ... all the fixed-width typedefs ?
I notice including <linux/types.h> in the U-Boot source tree and <stdint.h> provided by your compiler at the same time is a nightmare.
If we lean toward <stdint.h>, we must ban <linux/types.h>, but <stdint.h> is not available all the time. For example, kernel.org tool-chains do not provide <stdint.h>.
Maybe we can drastically re-write <linux/types.h> and friends to resolve the type conflicts, but I do not think we should not drift apart from the kernel because we have borrowed many source files from Linux.
Best Regards Masahiro Yamada