🚀 go-pugleaf

For some reason people always post things like this to comp.arch.  This
is a C question, not a computer architecture question.  The types
possessed by the underlying computer architecture need not correspond to
the types a given C compiler will support (particularly for "char" on
processors with no byte addressing).  Followups to comp.lang.c.

vanevery@rbdc.rbdc.com (Brandon Van every) writes:
>I'm writing some 3d graphics libraries that I want to be portable
>across all of the mainstream 32-bit and 64-bit architectures.  To this
>end, I've used GNU Autoconf to define the following data types with
>known bit lengths: char8, int16, int32, int64.

A good solution, most of the time.  Sometimes you can get bitten because
a given compiler/processor combo doesn't support a given size (e.g. int64).

>What I'm wondering, is how many mainstream CPU's out there are
>"strictly 64-bit," and have no 32-bit emulation of any kind.

You'd need to be more specific.  No 32-bit pointer types?  Or what?
Also, this is a compiler question, not an architecture question.
Several processors have no byte-manipulation instructions but have
C compilers that have an 8-bit char type.

>In the "mainstream" 64-bit universe, what are the typical bit sizes of
>the various integer types?  For example, nearly every 32-bit C/C++
>compiler in the universe does the following, nowadays:
>
>char	8 bits

There are a few mainframes with chars of a different size still around,
but in practice you don't need to care (except for DSP's which you may
not care about either).

>short	16 bits

Almost always true.

>int	32 bits

Whoops.  In 16-bit code for x86 processors, and for some 68k compilers
for embedded processors, int is 16 bits.

>long	32 bits

For 64-bit processors, long is often 64 bits (it is on the Alpha).

Some DSP processors make char = 32 bits and sizeof(int) 1 meaning int
is also 32 bits (and so is short).

Several compilers (including gcc, MIPS and others) add "long long" which is
usually 64 bits.
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