Initializing default values in a struct

Question

If I needed to initialize only a few select values of a C   struct  would this be correct   struct foo       foo     a true   b true         bool a      bool b      bool c     bar    Am I correct to assume I would end up with one struct item called bar with elements bar a   true  bar b   true and an undefined bar c

User · Answer

You don t even need to define a constructor  struct foo       bool a   true      bool b   true      bool c     bar    To clarify  these are called brace-or-equal-initializers  because you may also use brace initialization instead of equal sign   This is not only for aggregates  you can use this in normal class definitions  This was added in C  11

User · Answer

Yes  bar a and bar b are set to true  but bar c is undefined   However  certain compilers will set it to false   See a live example here  struct demo  According to C   standard Section 8 5 12      if no initialization is performed  an   object with automatic or dynamic storage duration has indeterminate value   For primitive built-in data types  bool  char  wchar t  short  int  long  float  double  long double   only global variables  all static storage variables  get default value of zero if they are not explicitly initialized   If you don t really want undefined bar c to start with  you should also initialize it like you did for bar a and bar b

User · Answer

An explicit default initialization can help   struct foo       bool a         bool b         bool c        bar    Behavior bool a    is same as bool b   bool    and return false

User · Answer

You can do it by using a constructor  like this       struct Date   int day  int month  int year   Date         day 0      month 0      year 0         or like this   struct Date   int day  int month  int year   Date   day 0          month 0          year 0         In your case bar c is undefined and its value depends on the compiler  while a and b were set to true

[c++] Initializing default values in a struct

Examples related to c++