①
class Hoge
public:
　Hoge(Piyo * pTarget)
　　: pTarget(pTarget) {}

private:
　Piyo * pTarget;
};

Piyo p;
const Piyo pc;
Hoge(&p);
Hoge(const_cast<Piyo *>(pc));

②
class Hoge
public:
　Hoge(Piyo * pTarget)
　　: pTarget(pTarget), pTargetConst(NULL) {}
　Hoge(const Piyo * pTarget)
　　: pTarget(NULL), pTargetConst(pTarget) {}
private:
　 Piyo * pTarget;
　const Piyo * pTargetConst;
};

Piyo p;
const Piyo pc;
Hoge h1(&p);
hoge h2(&pc);