Re: A question about postblit constructor

[Ferhat Kurtulmuş via Digitalmars-d-learn]

On Tuesday, 5 November 2019 at 10:13:59 UTC, Mike Parker wrote:
On Tuesday, 5 November 2019 at 08:47:05 UTC, Ferhat Kurtulmuş 
wrote:

value of int which is 0. I wonder how new memory is allocated 
without an explicit malloc here. Sorry for this noob question 
in advance, I could not find any doc mentioning a similar case.


    int* vals = cast(int*)malloc(len * S.sizeof);
    vals[0] = 4;
    vals[1] = 5;

    S s1 = S(vals, len);

    S s2 = s1;

    writeln(s2.vals[0]);

      writeln(s2.vals);
      writeln(s1.vals);

}

https://run.dlang.io/is/D0nfeT

Yep, it is obvious that my code is wrong. s1 and s2 point to the 
same memory address. I could obtain my desired behavior with copy 
constructor. The documentation also say "WARNING: The postblit is 
considered legacy and is not recommended for new code. Code 
should use copy constructors defined in the previous section".

struct S {
    int* vals;
    size_t length;

    this(ref return scope S another) {
        vals = cast(int*)malloc(another.length * S.sizeof);
        memcpy(vals, another.vals, another.length * S.sizeof);
        writeln("copied");
    }
    this(int* vls, size_t len){
        vals = vls;
        length = len;
    }

    ~this(){
        free(vals);
        writeln("freedooom!");
    }
}