Is it possible to avoid call to destructor for structs?

[Adrian Matoga]

On Sunday, 24 September 2017 at 19:52:52 UTC, bitwise wrote:
> On Sunday, 24 September 2017 at 17:11:26 UTC, Haridas wrote:
>> In the following code, Bar is an element of struct Foo. Is 
>> there a way to avoid a call to ~Bar when ~Foo is getting 
>> executed?
>>
>
> Don't construct it to begin with.
>
> struct Bar {
>     import std.stdio : writeln;
>     int a = 123;
>     void boink() { writeln(a); }
>     ~this(){ writeln("bar dtor"); }
> }
>
> struct Foo
> {
>     ubyte[Bar.sizeof] barBuffer;
>     Bar* _bar = null;
>
>     ref Bar bar()
>     {
>         import std.conv : emplace;
>
>         if(!_bar) {
>             _bar = cast(Bar*)barBuffer.ptr;
>             emplace(_bar);
>         }
>
>         return *_bar;
>     }
> }

You shouldn't store the pointer to barBuffer inside Foo. The 
language allows moving the structure around with a simple memcpy, 
so _bar is likely to point into garbage soon after it's assigned. 
Why don't you just return *cast(Bar*)barBuffer.ptr in bar()? You 
could still emplace a Bar inside barBuffer in Foo's constructor, 
if needed.