问题
I know this might be a basic question.
I have an assignment that requires me to understand what designated initializers in C are and what it means to initialize a variable with one. I am not familiar with the term and couldn't find any conclusive definitions. What is a designated initializer in C?
回答1:
Designated initialisers come in two flavours:
1) It provides a quick way of initialising specific elements in an array:
int foo[10] = { [3] = 1, [5] = 2 };
will set all elements to foo to 0, other than index 3 which will be set to 1 and index 5 which will be set to 2.
2) It provides a way of explicitly initialising struct members. For example, for
struct Foo { int a, b; };
you can write
struct Foo foo { .a = 1, .b = 2 };
Note that in this case, members that are not explicitly initialised are initialised as if the instance had static duration.
Both are standard C, but note that C++ does not support either (as constructors can do the job in that language.)
来源：https://stackoverflow.com/questions/47202557/what-is-a-designated-initializer-in-c