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This article mainly explains "Why do not implicitly capture this pointers in C++", interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Next, let the editor take you to learn "Why don't you implicitly capture this pointers in C++?"

F.54: if you need to capture this pointers, capture all variables explicitly (do not use implicit trapping).

Translator's note: implicit capture means that the variable name is ignored in the capture list, but only by using the same name as the variable outside the lamda expression. For example, in the negative sample code:

Auto lambda = [=] {use (I, x);}

Reason (reason)

This practice is difficult to understand. The capture list [=] in the member function looks like a value capture, but because it actually captures invisible this pointers as values, it actually captures data members by reference. If that's what you want to do, explicitly write this to the capture list.

Example (sample)

Class My_class {int x = 0; / /. Void f () {int I = 0; / /... Auto lambda = [=] {use (I, x);}; / / BAD: "looks like" copy/value capture / / [&] has identical semantics and copies the this pointer under the current rules / / [=, this] and [&, this] are not much better, and confusing x = 42; lambda (); / / calls use (0,42); x = 43; lambda (); / / calls use (0,43) / /... Auto lambda2 = [I, this] {use (I, x);}; / / ok, most explicit and least confusing / /...}}; Note (attention)

This is an issue that is less active in the standardization process and may be addressed by future versions of the standard by adding a new capture method or changing the meaning of [=]. At present, as long as it is clear.

Enforcement (implementation recommendations)

Prompt if the snap list of any lambda expression is defined to capture implicitly and at the same time capture the this pointer (either explicitly or by default).

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