What endiannesses do D support?

[Stewart Gordon]

On 04/10/2013 11:59, Denis Shelomovskij wrote:
> Some of druntime/phobos code assumes it is one of little/big endianness others have
> `static assert(0)` for third case. Lets clear the situation and make a decision.

Are you thinking of middle-endian orders such as 2,3,0,1?  Or just wondering in what 
situations neither BigEndian nor LittleEndian would be set?

I suppose that most, if not all, 32+-bit machines are either big-endian or little-endian. 
  But still, I imagine that the "third-case" is just a safeguard in case it is missed when 
somebody comes across a middle-endian platform and tries to compile that code on it.  Or 
maybe it was just put in out of belief that it is a good programming practice.

Endianness support as far as the D language is concerned doesn't seem to be clear-cut.
http://dlang.org/version.html
lists LittleEndian and BigEndian, but doesn't state that one of these will always be set. 
  So middle-endian machines, if a D compiler exists for them, would use this "third case". 
  Further work would be needed to determine what particular middle-endian order the 
machine implements for each size of integer.  (Floating points are even more complicated, 
so I guess you can't rely on any version flag to tell you about the format of these.)

OTOH, the platforms on which DMD runs are big-endian or little-endian.  If DMD is ported 
to a middle-endian platform, or the DMD Phobos/druntime code is cribbed for use with a 
third-party D compiler for a middle-endian machine, then the static assert will fire, 
thereby drawing attention to this unimplemented functionality rather than silently 
generating code that won't work because it's written for a little-endian machine, or for a 
big-endian machine.

Stewart.

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