std.variant doesn't do postblit/dtor correctly for large structs

[dlangBugzillaToGithub]

john.loughran.colvin (@John-Colvin) reported this on 2019-11-06T12:00:44Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=20360

CC List

• bugzilla (@WalterBright)

Description

unittest
{
    import std.variant;
    static struct S
    {
        int* p;
        ubyte[100] u;

        this(int a)
        {
            p = new int(a);
        }
    
        this(this)
        {
            p = new int(*p);
        }

        ~this()
        {
            p = null;
        }
    }
    Variant v = S(4);
    assert(v.peek!S.p !is null); // fails
}

[dlangBugzillaToGithub]

john.loughran.colvin commented on 2019-11-06T12:02:42Z

related to https://issues.dlang.org/show_bug.cgi?id=12944

[dlangBugzillaToGithub]

bugzilla (@WalterBright) commented on 2020-01-05T19:06:57Z

On my computer the static array u can contain up to 24 element to work. Together with the 8 bytes of the pointer this looks like 32 bytes is the magic border.