[Issue 7541] New: Postblit not called when returning from an array of structs.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7541

           Summary: Postblit not called when returning from an array of
                    structs.
           Product: D
           Version: D2
          Platform: All
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: johnaston.dev at gmail.com


--- Comment #0 from John Aston <johnaston.dev at gmail.com> 2012-02-19 03:20:58 PST ---
import std.stdio;

struct S
{
    string m_str = "defaultString";

    this(this)
    {
        writeln("In this(this)");
    }

    ~this()
    {
        writeln("In ~this():"~m_str);
    }

}

struct Holder
{
    S[] m_arr;
    S m_s;

    this(S[] arr)
    {
        m_arr = arr;
        m_s.m_str="H.m_s";
    }

    S getSMem()
    {
        return m_s;
    }

    S getSVec()
    {
        return m_arr[0];
    }

    S getSLocal()
    {
        S local = S("localString");
        return local;
    }
}

void main()
{
    Holder h = Holder(new S[1]);

    S s1 =  h.getSMem();
    S s2 =  h.getSVec();
    S s3 =  h.getSLocal();
}

The above in Windows D2.058 produces:

In this(this)
In ~this():localString
In ~this():defaultString
In ~this():H.m_s
In ~this():H.m_s


Only one postblit is produced in the above (from the getSMem() call).
The getSLocal() call can just move the struct.
However, getSVec() does not result in a postblit.
I noticed this in the context of a reference counting struct held in a
std.container.Array, and there were too few calls to this(this) compared to
~this().

This issue was discussed in:
http://stackoverflow.com/questions/9344579/why-is-thisthis-not-called-when-returning-from-array-of-structs

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