Bit-fields "In-class initialization" results in "error: lvalue required as left operand of assignment"

struct bitfield {
  int i = 0;  // ok
  int j : 8 = 0;  // error: lvalue required as left operand of assignment
};

What is the correct syntax to initialize bit-fields using C++11 "in-class initialization" feature?

Solution 1:

This was raised as Core Issue 1341 to the C++ standard, but was rejected by the C++ Core Working Group in October 2015 as NAD ("not a defect") - see http://open-std.org/JTC1/SC22/WG21/docs/cwg_closed.html#1341

Solution 2:

What is the correct syntax to initialize bit-fields using C++11 "in-class initialization" feature?

You cannot initialize bit-fields in-class. Paragraph 9.2 of the C++11 Standard specifies the grammar for class member declarators:

[...]

member-declarator:

declarator virt-specifier-seq(opt) pure-specifier(opt)

declarator brace-or-equal-initializer(opt)

identifier(opt) attribute-specifier-seq(opt): constant-expression

As you can see, declarators for bit-field members cannot be terminated by a brace-or-equal-initializer.