Here are a few pits I had the misfortune to fall into. All these have good reasons which I only understood after being bitten by behaviour that surprised me.
virtual functions in constructors aren't.
Don't violate the ODR (One Definition Rule), that's what anonymous namespaces are for (among other things).
Order of initialization of members depends on the order in which they are declared.
class bar {
vector vec_;
unsigned size_; // Note size_ declared *after* vec_
public:
bar(unsigned size)
: size_(size)
, vec_(size_) // size_ is uninitialized
{}
};
Default values and virtual have different semantics.
class base {
public:
virtual foo(int i = 42) { cout << "base " << i; }
};
class derived : public base {
public:
virtual foo(int i = 12) { cout << "derived "<< i; }
};
derived d;
base& b = d;
b.foo(); // Outputs `derived 42`
