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(dot) operator is used to access class, structure, or union members. The member is specified by a postfix expression, followed by a . (dot) operator, followed by a possibly qualified identifier or a pseudo-destructor name. (A pseudo-destructor is a destructor of a nonclass type.)
An initializer for a structure is a brace-enclosed comma-separated list of values, and for a union, a brace-enclosed single value. The initializer is preceded by an equal sign ( = ).
The only way you could determine if a struct was initialized would be to check each element within it to see if it matched what you considered an initialized value for that element should be.
Que: Can we initialize structure members within structure definition? No! We cannot initialize a structure members with its declaration, consider the given code (that is incorrect and compiler generates error).
This is a C99 feature that allows you to set specific fields of the struct by name in an initializer. Before this, the initializer needed to contain just the values, for all fields, in order -- which still works, of course.
So for the following struct:
struct demo_s {
int first;
int second;
int third;
};
...you can use
struct demo_s demo = { 1, 2, 3 };
...or:
struct demo_s demo = { .first = 1, .second = 2, .third = 3 };
...or even:
struct demo_s demo = { .first = 1, .third = 3, .second = 2 };
...though the last two are for C99 only.
These are C99's designated initializers.
Its known as designated initialisation (see Designated Initializers). An "initializer-list", Each '.' is a
"designator" which in this case names a particular member of the
'fuse_oprations' struct to initialize for the object designated by
the 'hello_oper' identifier.
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