Not sure if this is Phobos issue or DMD issue, but anyway...
std.stdio.writefln doesn't accept 'shared' variables correctly.

% cat shared.d
import std.stdio;

int a = 0;
shared int b = 0;

void main()
{
    writefln("a = [%d], b = [%d]", a, b);

    a = 42;
    b = 42;
    writefln("a = [%d], b = [%d]", a, b);
}
% dmd shared.d && ./shared
a = [0], b = []
a = [42], b = [*]
%

Note: '*' == chr(42)