phobos unittests not passing with dmd built by clang

Don Clugston dac at
Wed Feb 1 01:58:12 PST 2012

On 01/02/12 09:44, dennis luehring wrote:
>> The behaviour of the sign bit is completely specified in the x86
>> manuals. As that link says, the C standard got it wrong in a couple of
>> places.
>> The one thing which is implementation specific is that on Intel, an 80
>> bit load of a signalling NaN doesn't raise an exception, whereas it does
>> on AMD. I don't know what Via does.
> just a question:
> would it be a good idea to test this platform specific behavior
> in the phobos unit-tests?
> produce "an 80 bit load of a signalling NaN"
> check:
> intel: do not raise
> amd: do raise
> via: ...
> maybe only for showing that D is aware of this special cases?

It doesn't matter very much. If you load, and then do any operation 
(such as add) you'll get an exception. AMD will trigger one instruction 
Hardly anybody knows this -- I haven't found any references to it. It's 
in wikipedia, but the entry that mentions it was written by me!

There is an underlying problem we have though. What _is_ T.init?
If a variable of type T is default initialized as "this is 
uninitialized", what is T.init?

In most cases, the compiler should give you a "variable XXX is used 
before set" error anyway.

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