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c++c++11bit-fieldsin-class-initialization

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

  • 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.