Pure virtual functions in C++11

c++ c++11 virtual pure-virtual nullptr
fredoverflow picture fredoverflow · Dec 31, 2013 · Viewed 12.3k times · Source

In C++98, the null pointer was represented by the literal 0 (or in fact any constant expression whose value was zero). In C++11, we prefer nullptr instead. But this doesn't work for pure virtual functions:

struct X
{
    virtual void foo() = nullptr;
};

Why does this not work? Would it not make total sense? Is this simply an oversight? Will it be fixed?

Answer

Johannes Schaub - litb picture Johannes Schaub - litb · Dec 31, 2013

Because the syntax says 0, not expression or some other non-terminal matching nullptr.

For all the time only 0 has worked. Even 0L would be ill-formed because it does not match the syntax.

Edit

Clang allows = 0x0, = 0b0 and = 00 (31.12.2013). That is incorrect and should be fixed in the compiler, of course.

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