[D-runtime] dup attributes?

[Sean Kelly]

On Aug 6, 2010, at 5:03 AM, Steve Schveighoffer wrote:
> 
> Well, let me get to the root of the problem then :)
> 
> The issue is that phobos deals with void[] for things like I/O, which to me 
> seems like the correct type.  It allows you to pass in any array type without 
> casting, and it says "I don't know what type this is".  One of these functions 
> is std.file.read() which reads the entire file into an array and returns that 
> array as a void[].  Given that all the C functions use void *, it seems like the 
> right call.  But problems come in because void[] has the NO_SCAN bit cleared, 
> but this clearly has no pointers in it (the source is a file!).  So what to do?

The buffer can be passed around as void[] but the type that's allocated should be byte[] or ubyte[].  Allocating a void[] type will make the block scannable, which isn't desirable.

> std.file.read gets around this by calling gc_malloc directly.  However, it was 
> rightfully pointed out that if one simply dups the array, or uses concatenation 
> with it, it magically loses the NO_SCAN bit.  See the bug report here: 
> http://d.puremagic.com/issues/show_bug.cgi?id=4572

Is it really necessary to call gc_malloc() here?  Is the reason simply to avoid the zero initialization?