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digitalmars.D.bugs - [Issue 7280] New: Can't get address of array `.length` or `.ptr` properties

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7280

           Summary: Can't get address of array `.length` or `.ptr`
                    properties
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: minor
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: verylonglogin.reg gmail.com


--- Comment #0 from Denis <verylonglogin.reg gmail.com> 2012-01-12 20:06:56 MSK
---
---
void f() {
    void[] arr;
    size_t* _length = &arr.length; // Error: arr.length is not an lvalue
    void** _ptr = &arr.ptr;        // Error: cast(void*)arr is not an lvalue
}
---
What is the case not to behave like a struct of two elements?

Workaround:
---
size_t* arrayLengthRef(T)(ref T[] arr) {
    return (cast(size_t*)&arr);
}

T** arrayPtrRef(T)(ref T[] arr) {
    return (cast(T**)&arr) + 1;
}
---

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parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7280


Steven Schveighoffer <schveiguy yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |schveiguy yahoo.com
         Resolution|                            |WONTFIX


--- Comment #1 from Steven Schveighoffer <schveiguy yahoo.com> 2012-01-12
10:17:01 PST ---
arr.length is a read/write property.  Writing length is not a simple field set,
it calls a runtime function.
arr.ptr is a read only property.

Setting these must be done in tandem, and is done via the slicing interface or
via the length set operation.  You can circumvent as you say, but it should not
be easy, since it is very dangerous.

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