memory management - Why this function return an (owned) value? -


the code from: genie howto repeat string n times string arraygenie howto repeat string n times string array

def repeatwithsep (e: string, n: int, separator: string): string     var elen = e.length;     var slen = separator.length;     var = new stringbuilder.sized ((elen * n) + (slen * (n - 1)) + 1);     var = 0 (n - 1)         if != 0             a.append_len (separator, slen)         a.append_len (e, elen)     return (owned) a.str

var a local variable, when a goes out of scope, destroyed. why function

return (owned) a.str

what difference between

return a.str

return (owned) a.str

what benefit of (owned)

return a.str make copy of string using g_strdup, because default function result , stringbuilder both own separate copy of string after (implicit) assignment.

since stringbuilder stored in a go out of scope , it's copy never used again not desireable / efficient in case.

hence solution pass ownership of string a.str result of function using (owned) directive.

btw: can find out compiling both versions valac -c , comparing generated c code:

-       _tmp21_->str = null; -       result = _tmp22_; +       _tmp23_ = g_strdup (_tmp22_); +       result = _tmp23_;

(in comparison left side return (owned) a.str , right side return a.str)

ps: documented in ownership section of vala tutorial , corresponding part of genie tutorial.

i recommend reference handling article.


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