core/internal/postblit.d

/**
 This module contains support for D's postblit feature

  Copyright: Copyright Digital Mars 2000 - 2019.
  License: Distributed under the
       $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost Software License 1.0).
     (See accompanying file LICENSE)
  Source: $(DRUNTIMESRC core/_internal/_destruction.d)
*/
module core.internal.postblit;

// compiler frontend lowers struct array postblitting to this
void __ArrayPostblit(T)(T[] a)
{
    foreach (ref T e; a)
        e.__xpostblit();
}

package void postblitRecurse(S)(ref S s)
    if (is(S == struct))
{
    static if (__traits(hasMember, S, "__xpostblit") &&
               // Bugzilla 14746: Check that it's the exact member of S.
               __traits(isSame, S, __traits(parent, s.__xpostblit)))
        s.__xpostblit();
}

package void postblitRecurse(E, size_t n)(ref E[n] arr)
{
    import core.internal.destruction: destructRecurse;
    import core.internal.traits : hasElaborateCopyConstructor;

    static if (hasElaborateCopyConstructor!E)
    {
        size_t i;
        scope(failure)
        {
            for (; i != 0; --i)
            {
                destructRecurse(arr[i - 1]); // What to do if this throws?
            }
        }

        for (i = 0; i < arr.length; ++i)
            postblitRecurse(arr[i]);
    }
}

// Test destruction/postblit order
@safe nothrow pure unittest
{
    string[] order;

    struct InnerTop
    {
        ~this() @safe nothrow pure
        {
            order ~= "destroy inner top";
        }

        this(this) @safe nothrow pure
        {
            order ~= "copy inner top";
        }
    }

    struct InnerMiddle {}

    version (none) // https://issues.dlang.org/show_bug.cgi?id=14242
    struct InnerElement
    {
        static char counter = '1';

        ~this() @safe nothrow pure
        {
            order ~= "destroy inner element #" ~ counter++;
        }

        this(this) @safe nothrow pure
        {
            order ~= "copy inner element #" ~ counter++;
        }
    }

    struct InnerBottom
    {
        ~this() @safe nothrow pure
        {
            order ~= "destroy inner bottom";
        }

        this(this) @safe nothrow pure
        {
            order ~= "copy inner bottom";
        }
    }

    struct S
    {
        char[] s;
        InnerTop top;
        InnerMiddle middle;
        version (none) InnerElement[3] array; // https://issues.dlang.org/show_bug.cgi?id=14242
        int a;
        InnerBottom bottom;
        ~this() @safe nothrow pure { order ~= "destroy outer"; }
        this(this) @safe nothrow pure { order ~= "copy outer"; }
    }

    string[] destructRecurseOrder;
    {
        import core.internal.destruction: destructRecurse;

        S s;
        destructRecurse(s);
        destructRecurseOrder = order;
        order = null;
    }

    assert(order.length);
    assert(destructRecurseOrder == order);
    order = null;

    S s;
    postblitRecurse(s);
    assert(order.length);
    auto postblitRecurseOrder = order;
    order = null;
    S s2 = s;
    assert(order.length);
    assert(postblitRecurseOrder == order);
}

@safe unittest
{
    // Bugzilla 14746
    static struct HasPostblit
    {
        this(this) { assert(0); }
    }
    static struct Owner
    {
        HasPostblit* ptr;
        alias ptr this;
    }

    Owner o;
    assert(o.ptr is null);
    postblitRecurse(o);     // must not reach in HasPostblit.__postblit()
}

// Test handling of fixed-length arrays
// Separate from first test because of https://issues.dlang.org/show_bug.cgi?id=14242
@safe unittest
{
    string[] order;

    struct S
    {
        char id;

        this(this)
        {
            order ~= "copy #" ~ id;
        }

        ~this()
        {
            order ~= "destroy #" ~ id;
        }
    }

    string[] destructRecurseOrder;
    {
        import core.internal.destruction: destructRecurse;

        S[3] arr = [S('1'), S('2'), S('3')];
        destructRecurse(arr);
        destructRecurseOrder = order;
        order = null;
    }
    assert(order.length);
    assert(destructRecurseOrder == order);
    order = null;

    S[3] arr = [S('1'), S('2'), S('3')];
    postblitRecurse(arr);
    assert(order.length);
    auto postblitRecurseOrder = order;
    order = null;

    auto arrCopy = arr;
    assert(order.length);
    assert(postblitRecurseOrder == order);
}

// Test handling of failed postblit
// Not nothrow or @safe because of https://issues.dlang.org/show_bug.cgi?id=14242
/+ nothrow @safe +/ unittest
{
    static class FailedPostblitException : Exception { this() nothrow @safe { super(null); } }
    static string[] order;
    static struct Inner
    {
        char id;

        @safe:
        this(this)
        {
            order ~= "copy inner #" ~ id;
            if (id == '2')
                throw new FailedPostblitException();
        }

        ~this() nothrow
        {
            order ~= "destroy inner #" ~ id;
        }
    }

    static struct Outer
    {
        Inner inner1, inner2, inner3;

        nothrow @safe:
        this(char first, char second, char third)
        {
            inner1 = Inner(first);
            inner2 = Inner(second);
            inner3 = Inner(third);
        }

        this(this)
        {
            order ~= "copy outer";
        }

        ~this()
        {
            order ~= "destroy outer";
        }
    }

    auto outer = Outer('1', '2', '3');

    try postblitRecurse(outer);
    catch (FailedPostblitException) {}
    catch (Exception) assert(false);

    auto postblitRecurseOrder = order;
    order = null;

    try auto copy = outer;
    catch (FailedPostblitException) {}
    catch (Exception) assert(false);

    assert(postblitRecurseOrder == order);
    order = null;

    Outer[3] arr = [Outer('1', '1', '1'), Outer('1', '2', '3'), Outer('3', '3', '3')];

    try postblitRecurse(arr);
    catch (FailedPostblitException) {}
    catch (Exception) assert(false);

    postblitRecurseOrder = order;
    order = null;

    try auto arrCopy = arr;
    catch (FailedPostblitException) {}
    catch (Exception) assert(false);

    assert(postblitRecurseOrder == order);
}