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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