[Issue 22271] New: Appending to an empty array reallocate

d-bugmail at puremagic.com d-bugmail at puremagic.com
Fri Sep 3 14:20:15 UTC 2021


          Issue ID: 22271
           Summary: Appending to an empty array reallocate
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: deadalnix at gmail.com

See sample code:

string x = "foobar";
string y;
y ~= x;

import std.stdio;
writefln("%x %x", x.ptr, y.ptr);

We can see here that a new allocation is done and the content of x copied in
it. However, this reallocation is superfluous and a waste of perfectly good CPU
cycles and memory :)


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