At 57:30, the use of brace initialization for the vector will result in its constructor with initializer_list being the best viable function. Hence, it creates a vector with one element, size.
43:03 the example I always go to about where self assignment could occur is in a buggy implementation of quicksort. If the algorithm to swap values around the pivot is not implemented correctly and one has an odd number of elements, the buggy algorithm may decide to swap the last item (where both the high and low cursors point to the same value); after all, any value should not be less than itself if std::less is being used. "just don't get into a situation where self-assignment is possible" is nice in theory, but in real codebases (especially with template code) it happens, and it's preferable to limp along with misuse of the assignment operator than it is to blow up in a strange way.
33:33 If the copy assignment operator is implemented as it is written on the slide, this is a good point where pass by value can simplify the code a little bit: Widget(Widget other). But passing by reference brings some flexibility and we can check some conditions as it was done at 33:55.
I wish this went over the ordering of the initialization and deletion because I keep getting clang-tidy warnings about initialization order and it's quite confusing.
Without further information then there has to be a certain amount of guessing going on. The most common initialisation order issue is where members are not initialised in the same order as they are declared. struct s { s() : b(0), a(1) {} int a; int b; }; The reason why this is an issue is that the compiler will initialise members in the order that they are declared, not the order that the constructor initialises them in the initialiser list. So as an example, what do you think would happen if the constructor was: s() : b(0), a(b) {} ? If you guess that a will contain an undefined value then congratulations.
If you write a base class, and therefore (as per best practices) declare a _virtual_ destructor even if it doesn't actually do anything, does that mean you then have to explicitly provide (or declare =default) the copy constructors as well? I've seen cases where a new abstract base class with a virtual destructor is defined, just for this purpose, and then the other 5 special member functions are =default - but that seems onerous to do every single time one wants to write a potential base class.
What happen if put destructor in private: and call them by member function as pointer; Like private : ~Widget(){//…….//} Public: ….. ….. Void deleted(){ this->~Widget();} } Than you can call it or not call it … Is there other trick about it , what happen if not deleted or not call it.
Great talk! Whether it's a B2B or more advanced topic, Klaus has a great way explaining things.
Glad you enjoyed it!
I feel Klaus is the only person who bring contents which every C++ programmer needs. Great presenter !!
Love watching Klaus explaining things to the point! Thanks for doing this 👍
Glad you enjoyed it!
To be honest, imho Klaus You are the best lecturer on cppcon. Great job!
Absolutely Amazing!
You are my c++ teacher
At 57:30, the use of brace initialization for the vector will result in its constructor with initializer_list being the best viable function. Hence, it creates a vector with one element, size.
Klaus is the best❤ thanks for sharing videos and classifying “back to basic” on the playlist! It has helped beginners like me a lot ❤appreciate it 🌸
Excellent talk, as always from Klaus.
Thanks for listening
You are an amazing teacher!
Great talk. Idk how i can thank you cppcon and esp Klaus.
43:03 the example I always go to about where self assignment could occur is in a buggy implementation of quicksort. If the algorithm to swap values around the pivot is not implemented correctly and one has an odd number of elements, the buggy algorithm may decide to swap the last item (where both the high and low cursors point to the same value); after all, any value should not be less than itself if std::less is being used.
"just don't get into a situation where self-assignment is possible" is nice in theory, but in real codebases (especially with template code) it happens, and it's preferable to limp along with misuse of the assignment operator than it is to blow up in a strange way.
33:33 If the copy assignment operator is implemented as it is written on the slide, this is a good point where pass by value can simplify the code a little bit: Widget(Widget other). But passing by reference brings some flexibility and we can check some conditions as it was done at 33:55.
Vielen Dank, Klaus!
=delete
Does not delist the function but to disable it.
Only shit I hope committee try another keyword instead, this answers a bunch of my problems..
Lots of slides where the author has written "delete resource" instead of "delete pr".
I wish this went over the ordering of the initialization and deletion because I keep getting clang-tidy warnings about initialization order and it's quite confusing.
Without further information then there has to be a certain amount of guessing going on. The most common initialisation order issue is where members are not initialised in the same order as they are declared.
struct s
{
s() : b(0), a(1) {}
int a;
int b;
};
The reason why this is an issue is that the compiler will initialise members in the order that they are declared, not the order that the constructor initialises them in the initialiser list. So as an example, what do you think would happen if the constructor was:
s() : b(0), a(b) {}
?
If you guess that a will contain an undefined value then congratulations.
Greta talk... but is it okay to declare your copy constructor as Widget(const Widget& someVar)?
#56.00 Assignment operation needs to return *this because it is required in cascaded assignment
If you write a base class, and therefore (as per best practices) declare a _virtual_ destructor even if it doesn't actually do anything, does that mean you then have to explicitly provide (or declare =default) the copy constructors as well?
I've seen cases where a new abstract base class with a virtual destructor is defined, just for this purpose, and then the other 5 special member functions are =default - but that seems onerous to do every single time one wants to write a potential base class.
I was going to ask the same thing.
What happen if put destructor in private: and call them by member function as pointer;
Like private : ~Widget(){//…….//}
Public:
…..
…..
Void deleted(){ this->~Widget();}
}
Than you can call it or not call it …
Is there other trick about it , what happen if not deleted or not call it.
Finally, the truth about =delete; The function exists but is disabled. Unfortunate naming.