5 ms·

int i; does not initialize the value.

kstrauser 1y ago
It's a gotcha to be sure. Sometimes it does, sometimes it doesn't. From a reference[0]: #include <string> struct T1 { int mem; }; struct T2 { int mem; T2() {} // “mem” is not in the initializer list }; int n; // static non-class, a two-phase initialization is done: // 1) zero-initialization initializes n to zero // 2) default-initialization does nothing, leaving n being zero int main() { [[maybe_unused]] int n; // non-class, the value is indeterminate std::string s; // class, calls default constructor, the value is "" std::string a[2]; // array, default-initializes the elements, the value is {"", ""} // int& r; // Error: a reference // const int n; // Error: a const non-class // const T1 t1; // Error: const class with implicit default constructor [[maybe_unused]] T1 t1; // class, calls implicit default constructor const T2 t2; // const class, calls the user-provided default constructor // t2.mem is default-initialized } That `int n;` on the 11th line is initialized to 0 per standard. `int n;` on line 18, inside a function, is not. And `struct T1 { int mem; };` on line 3 will have `mem` initialized to 0 if `T1` is instantiated like `T1 t1{};`, but not if it's instantiated like `T1 t1;`. There's no way to tell from looking at `struct T1{...}` how the members will be initialized without knowing how they'll be called. C++ is fun! [0]https://en.cppreference.com/w/cpp/language/default_initialization https://en.cppreference.com/w/cpp/language/default_initializ...
- 90s_dev 1y ago
  Stroustrup once said > "There's a great language somewhere deep inside of C++" or something to that effect.
  - int_19h 1y ago
    Yes, it's called Simula-67. (the original pre-ISO C++ is basically C with Simula bolted onto it.)
portaltonowhere 1y ago
Unless `i` is global…

It's a gotcha to be sure. Sometimes it does, sometimes it doesn't. From a reference[0]: #include <string> struct T1 { int mem; }; struct T2 { int mem; T2() {} // “mem” is not in the initializer list }; int n; // static non-class, a two-phase initialization is done: // 1) zero-initialization initializes n to zero // 2) default-initialization does nothing, leaving n being zero int main() { [[maybe_unused]] int n; // non-class, the value is indeterminate std::string s; // class, calls default constructor, the value is "" std::string a[2]; // array, default-initializes the elements, the value is {"", ""} // int& r; // Error: a reference // const int n; // Error: a const non-class // const T1 t1; // Error: const class with implicit default constructor [[maybe_unused]] T1 t1; // class, calls implicit default constructor const T2 t2; // const class, calls the user-provided default constructor // t2.mem is default-initialized } That `int n;` on the 11th line is initialized to 0 per standard. `int n;` on line 18, inside a function, is not. And `struct T1 { int mem; };` on line 3 will have `mem` initialized to 0 if `T1` is instantiated like `T1 t1{};`, but not if it's instantiated like `T1 t1;`. There's no way to tell from looking at `struct T1{...}` how the members will be initialized without knowing how they'll be called. C++ is fun! [0]https://en.cppreference.com/w/cpp/language/default_initialization https://en.cppreference.com/w/cpp/language/default_initializ...

90s_dev 1y ago
Stroustrup once said > "There's a great language somewhere deep inside of C++" or something to that effect.
- int_19h 1y ago
  Yes, it's called Simula-67. (the original pre-ISO C++ is basically C with Simula bolted onto it.)

portaltonowhere 1y ago

Unless `i` is global…