tree 4e44fd99d23f9ca0ce09d62cc51f3c3b392229de
parent 8f4dbaab648e587b28c658e12ab0b4e943f1d544
author Masahiro Yamada <yamada.masahiro@socionext.com> 1517551776 +0900
committer Masahiro Yamada <yamada.masahiro@socionext.com> 1524821702 +0900

types: use int-ll64 for both aarch32 and aarch64

Since commit 031dbb122472 ("AArch32: Add essential Arch helpers"),
it is difficult to use consistent format strings for printf() family
between aarch32 and aarch64.

For example, uint64_t is defined as 'unsigned long long' for aarch32
and as 'unsigned long' for aarch64.  Likewise, uintptr_t is defined
as 'unsigned int' for aarch32, and as 'unsigned long' for aarch64.

A problem typically arises when you use printf() in common code.

One solution could be, to cast the arguments to a type long enough
for both architectures.  For example, if 'val' is uint64_t type,
like this:

  printf("val = %llx\n", (unsigned long long)val);

Or, somebody may suggest to use a macro provided by <inttypes.h>,
like this:

  printf("val = %" PRIx64 "\n", val);

But, both would make the code ugly.

The solution adopted in Linux kernel is to use the same typedefs for
all architectures.  The fixed integer types in the kernel-space have
been unified into int-ll64, like follows:

    typedef signed char           int8_t;
    typedef unsigned char         uint8_t;

    typedef signed short          int16_t;
    typedef unsigned short        uint16_t;

    typedef signed int            int32_t;
    typedef unsigned int          uint32_t;

    typedef signed long long      int64_t;
    typedef unsigned long long    uint64_t;

[ Linux commit: 0c79a8e29b5fcbcbfd611daf9d500cfad8370fcf ]

This gets along with the codebase shared between 32 bit and 64 bit,
with the data model called ILP32, LP64, respectively.

The width for primitive types is defined as follows:

                   ILP32           LP64
    int            32              32
    long           32              64
    long long      64              64
    pointer        32              64

'long long' is 64 bit for both, so it is used for defining uint64_t.
'long' has the same width as pointer, so for uintptr_t.

We still need an ifdef conditional for (s)size_t.

All 64 bit architectures use "unsigned long" size_t, and most 32 bit
architectures use "unsigned int" size_t.  H8/300, S/390 are known as
exceptions; they use "unsigned long" size_t despite their architecture
is 32 bit.

One idea for simplification might be to define size_t as 'unsigned long'
across architectures, then forbid the use of "%z" string format.
However, this would cause a distortion between size_t and sizeof()
operator.  We have unknowledge about the native type of sizeof(), so
we need a guess of it anyway.  I want the following formula to always
return 1:

  __builtin_types_compatible_p(size_t, typeof(sizeof(int)))

Fortunately, ARM is probably a majority case.  As far as I know, all
32 bit ARM compilers use "unsigned int" size_t.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>