C Lambda Capture By Reference Lifetime

Consider the following code.

C lambda capture by reference lifetime. I know that if a lambda captures a reference variable by value the referenced object will be. This also means that the lambda can modify this without being declared mutable. Also their modification will affect value of outer scope variables because they are captured by reference. If the lambda out lives the lifetime of the object that created it the lambda can become invalid.

Reference captures introduce a lifetime dependency but value captures have no lifetime dependencies. As such the lambda does not own this. Be extra careful when you capture variables by reference especially with a default reference capture. If you capture a local by reference in an async lambda that local will very possibly be gone by the time the lambda runs resulting in an access violation at run time.

When you capture by reference the lambda function is capable of modifying the local variable outside the lambda function it is after all a reference. If we want the captured name to be valid when the lambda is used we need to capture it by value instead either explicitly or using a default capture by value. Already and it does not answer this question. Those data members that correspond to captures without initializers.

Assume that the referenced value outlives the lambda but not the scope in which the lamdba gets created. I have read what is the lifetime of lambda derived implicit functors in c. Dangers and benefits of capture by reference. Now the variables specified in capture list will be captured inside lambda by reference.

Lambda functions are quite an intuitive concept of modern c introduced in c 11 so there are already tons of articles on lambda function tutorials over the internet. This is especially important when the lambda runs asynchronously. For a lambda i d like to capture something by reference which was held in the outer scope by reference already. I understand that c lambda syntax is just sugar for making an instance of an anonymous class with a call operator and some state and i understand the lifetime requirements of that state decided by whether you capture by value of by reference.

The captured variables must outlive the lambda. If the lambda expression captures anything by copy either implicitly with capture clause or explicitly with a capture that does not include the character e g. Inside lambda they can be accessed and their value can also be changed. It is the pointer which is const not the object being pointed to.

Lambda capture and object lifetime someone brought up an issue in comp lang c today that might be unexpected enough to some that it warrants discussion.