http://d.puremagic.com/issues/show_bug.cgi?id=8901

           Summary: a bug to cast from array literal to ubyte[]
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: enjouzensyou.boinc@gmail.com


--- Comment #0 from Kazuki Komatsu <enjouzensyou.boinc@gmail.com> 2012-10-27 06:22:19 PDT ---
import std.stdio;

void main()
{
    int a = 12321;
    int[] arr = [a];

    assert( (cast(ubyte[])[a])
                == (cast(ubyte[])arr) );
}


This code doesn't work!

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hsteoh@quickfur.ath.cx changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hsteoh@quickfur.ath.cx


--- Comment #1 from hsteoh@quickfur.ath.cx 2012-10-27 13:21:36 PDT ---
I don't understand, why should this work?

D arrays are not the same as C arrays; casting an int into an array does not magically make it an array of bytes.

If you want to get the byte representation, you need to do something like this:

int a = 1234;
ubyte* ptr = cast(ubyte*)&a;
writeln(ptr[0 .. int.sizeof]);

Note, though, that this is unsafe, and is generally not recommended in D code, unless you're writing low-level code.

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hsteoh@quickfur.ath.cx changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


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--- Comment #2 from hsteoh@quickfur.ath.cx 2012-10-27 13:26:15 PDT ---
Haha, case in point: that slice operation should be ptr[0 .. int.sizeof-1].

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--- Comment #3 from hsteoh@quickfur.ath.cx 2012-10-27 13:27:15 PDT ---
Oh wait, no, the original was correct. :-/  See what I mean? It's unsafe. :)

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SHOO <zan77137@nifty.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |zan77137@nifty.com
         Resolution|INVALID                     |


--- Comment #4 from SHOO <zan77137@nifty.com> 2012-10-28 04:54:11 PDT ---
This is like the bug somehow or other. However, by the document of the Web, it does not seem to be touched about the explicit cast from array to array deeply. In the current implementation, it is worked by _d_arraycast in druntime. The cast is performed safely, and it throws Error if misalignment occurs.

This bug seems to happen, because `cast(ubyte[])[a]` is processed as
`cast(ubyte[])[cast(ubyte)a]` by dmd.
`[a]` should be always processed as `int[]`.

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yebblies <yebblies@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
                 CC|                            |yebblies@gmail.com
         Resolution|                            |INVALID


--- Comment #5 from yebblies <yebblies@gmail.com> 2012-10-29 05:19:42 EST ---
(In reply to comment #4)
> 
> This bug seems to happen, because `cast(ubyte[])[a]` is processed as
> `cast(ubyte[])[cast(ubyte)a]` by dmd.
> `[a]` should be always processed as `int[]`.

That is not a bug, casting an array literal is not the same as casting an array/slice.  While this is an inconsistent design, it is definitely intentional.

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