[U-Boot] [OpenQuestion] stdint.h and inttypes.h in U-Boot ?

[Masahiro Yamada]

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 at 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