http://d.puremagic.com/issues/show_bug.cgi?id=4789

           Summary: std.algorithm.sort bug
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: soarowl@yeah.net


--- Comment #0 from soarowl@yeah.net 2010-09-02 19:39:54 PDT ---
private import
    std.algorithm,
    std.stdio;

void main()
{
    int[2][] a;
    a ~= [1, 2];
    a ~= [2, 3];
    a ~= [3, 4];
    a ~= [1, 1];

    std.algorithm.sort(a);
    std.stdio.writefln("%s", a);
}


When I compile without any arguments, the runtime has an "object.Exception: overlapping array copy" exception;

But when I compile with -release or -release -inline arguments, the result is correct.

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David Simcha <dsimcha@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |dsimcha@yahoo.com
         Resolution|                            |FIXED


--- Comment #1 from David Simcha <dsimcha@yahoo.com> 2010-09-02 20:52:24 PDT ---
Here's the swap algorithm used in the int[] instantiation in std.algorithm:

auto t = a;
a = b;
b = t;

This function is broken for static arrays if a and b are the same array, and in your example, swap() gets called with the rhs and lhs being the same array. This is probably related to using optimized memcpy() routines under the hood for copying static arrays.  The language should arguably do the right thing when a static array is assigned to itself instead of this kind of crazy behavior.

In the mean time, I've inserted a trivial check into swap() that only gets compiled in for static arrays.  It's a kludge, but it's a trivial, well-encapsulated kludge and can be removed when the deeper issue gets solved.

http://dsource.org/projects/phobos/changeset/1948

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dawg@dawgfoto.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |dawg@dawgfoto.de
         Resolution|FIXED                       |


--- Comment #2 from dawg@dawgfoto.de 2011-01-11 05:44:43 PST ---
import std.traits : hasElaborateAssign;
import std.algorithm : swap;

struct Elem {
  ~this() {}
}
static assert(hasElaborateAssign!Elem);

void main() {
  auto elem = Elem();
  swap(elem, elem);
}

----

This bug still exists for structs with elaborate assign.

It throws an "object.Exception: overlapping array copy".

Before changeset 1948 the implementation used memcpy which would have also led
to undefined behavior on some platforms.
Now swap uses _d_arraycopy which throws the overlapping exception.

Proposed fix is to add an "if (lhs !is rhs)" around the struct copy code.

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--- Comment #3 from dawg@dawgfoto.de 2011-01-11 05:50:48 PST ---
> Before changeset 1948 the implementation used memcpy which would have also led to undefined behavior on some platforms.
This was changeset 2180 that changed the implementation. But as stated is essentially broken in both versions.

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dawg@dawgfoto.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |DUPLICATE


--- Comment #4 from dawg@dawgfoto.de 2011-06-18 20:07:44 PDT ---
*** This issue has been marked as a duplicate of issue 5705 ***

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