Pop quiz [memory usage]

[Jarrett Billingsley]

On Sat, Jun 6, 2009 at 8:03 AM, Vladimir
Panteleev<thecybershadow at gmail.com> wrote:
> // Works for DMD1/Phobos, DMD1/Tango and DMD2/Phobos
> version(Tango) import tango.io.Console;
> else           import std.stdio;
>
> struct S
> {
>        ubyte[40_000] data;
> }
>
> void main()
> {
>        S[] a;
>        a ~= S();
>
>        // QUESTION: How much memory will this program consume upon reaching
> this point?
>        version(Tango) Cin.copyln();
>        else           readln();
> }
>

There seems to be something wrong with the newCapacity function that
_d_arrayappendcT calls.  From an element size of 20000 (I halved it
just to make the allocation faster) and an array length of 1, it
somehow calculates the new size to be 266686600.  Hm.  That seems a
bit off.

It seems this line:

long mult = 100 + (1000L * size) / log2plus1(newcap);

is to blame.  I don't think large value types were taken into account
here.  The resulting multiplier is 1,333,433, which is hilariously
large.