in-class initialization for this pointer doesn't work on CRTP.

[llvmbot]

Bugzilla Link	19218
Version	3.4
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor

Extended Description

template <class Derived>
class base
{
    Derived* _ptr{static_cast<Derived*>(this)};
};

class test
    : public base<test>
{
};

The above code doesn't compile.

However if one is to write a custom constructor as follow it would work:

template <class Derived>
class base
{
public:
    base() : _ptr{static_cast<Derived>(this)} {}
private:
    Derived* _ptr{};
};

Not sure if true, but I vaguely remember that in-class initialization should have the same side-effect as constructor initialization lists.

[Endilll]

Accepted since Clang 3.6: https://godbolt.org/z/cdhMqjP5e

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (llvmbot)

| | | | --- | --- | | Bugzilla Link | [19218](https://llvm.org/bz19218) | | Version | 3.4 | | OS | Linux | | Reporter | LLVM Bugzilla Contributor | | CC | @DougGregor |

Extended Description

template <class Derived>
class base
{
    Derived* _ptr{static_cast<Derived*>(this)};
};

class test
    : public base<test>
{
};

The above code doesn't compile.

However if one is to write a custom constructor as follow it would work:

template <class Derived>
class base
{
public:
    base() : _ptr{static_cast<Derived>(this)} {}
private:
    Derived* _ptr{};
};

Not sure if true, but I vaguely remember that in-class initialization should have the same side-effect as constructor initialization lists.