CODEWITHSUNDEEP
constructorresourcesdestructord
porton
porton

Reputation: 5805

RAI in D for structs, avoiding expensive copying

I am a novice in D programming language. I am going to write some bindings of a C library in D. So this question.

Suppose we have a struct S (not class!)

Suppose all of the following are expensive operations:

Now I want to pass S values around like this:

S func(const ref S x) {
    return S(x);
}

Question: Will excessive (more than minimally enough to express my algorithm) use of the above expensive operations happen? If yes, how to prevent this?

Note that I use struct rather than class from practical performance reasons.

Upvotes: 0

Views: 57

Answers (1)

porton
porton

Reputation: 5805

The following program shows that excessive copying does happen:

$ ./init_test 
Initialization
Postblit
Finalization
Finalization

Program text:

import std.stdio;

struct Expensive {
    static create() {
        writeln("Initialization");
        return Expensive.init;
    }
    ~this() {
        writeln("Finalization");
    }
    this(this) {
        writeln("Postblit");
    }
}
    
Expensive func(const Expensive x) { // `ref const` results in compilation error
    return x;
}
    
void main() {
    Expensive obj = func(Expensive.create());
}

Upvotes: 0

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