book

Effective Modern C++

by Scott Meyers

November 2014

Intermediate to advanced

336 pages

9h 37m

English

O'Reilly Media, Inc.

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Using Code ExamplesSafari® Books OnlineHow to Contact Us
Terminology and ConventionsReporting Bugs and Suggesting Improvements
Item 1: Understand template type deduction.Case 1: ParamType is a Reference or Pointer, but not a Universal ReferenceCase 2: ParamType is a Universal ReferenceCase 3: ParamType is Neither a Pointer nor a ReferenceArray ArgumentsFunction ArgumentsItem 2: Understand auto type deduction.Item 3: Understand decltype.Item 4: Know how to view deduced types.IDE EditorsCompiler DiagnosticsRuntime Output
Item 5: Prefer auto to explicit type declarations.Item 6: Use the explicitly typed initializer idiom when auto deduces undesired types.
Item 7: Distinguish between () and {} when creating objects.Item 8: Prefer nullptr to 0 and NULL.Item 9: Prefer alias declarations to typedefs.Item 10: Prefer scoped enums to unscoped enums.Item 11: Prefer deleted functions to private undefined ones.Item 12: Declare overriding functions override.Item 13: Prefer const_iterators to iterators.Item 14: Declare functions noexcept if they won’t emit exceptions.Item 15: Use constexpr whenever possible.Item 16: Make const member functions thread safe.Item 17: Understand special member function generation.
Item 18: Use std::unique_ptr for exclusive-ownership resource management.Item 19: Use std::shared_ptr for shared-ownership resource management.Item 20: Use std::weak_ptr for std::shared_ptr-like pointers that can dangle.Item 21: Prefer std::make_unique and std::make_shared to direct use of new.Item 22: When using the Pimpl Idiom, define special member functions in the implementation file.
Item 23: Understand std::move and std::forward.Item 24: Distinguish universal references from rvalue references.Item 25: Use std::move on rvalue references, std::forward on universal references.Item 26: Avoid overloading on universal references.Item 27: Familiarize yourself with alternatives to overloading on universal references.Abandon overloadingPass by const T&Pass by valueUse Tag dispatchConstraining templates that take universal referencesTrade-offsItem 28: Understand reference collapsing.Item 29: Assume that move operations are not present, not cheap, and not used.Item 30: Familiarize yourself with perfect forwarding failure cases.Braced initializers0 or NULL as null pointersDeclaration-only integral static const and constexpr data membersOverloaded function names and template namesBitfieldsUpshot
Item 31: Avoid default capture modes.Item 32: Use init capture to move objects into closures.Item 33: Use decltype on auto&& parameters to std::forward them.Item 34: Prefer lambdas to std::bind.

Item 35: Prefer task-based programming to thread-based.Item 36: Specify std::launch::async if asynchronicity is essential.Item 37: Make std::threads unjoinable on all paths.Item 38: Be aware of varying thread handle destructor behavior.Item 39: Consider void futures for one-shot event communication.Item 40: Use std::atomic for concurrency, volatile for special memory.
Item 41: Consider pass by value for copyable parameters that are cheap to move and always copied.Item 42: Consider emplacement instead of insertion.

Content preview from Effective Modern C++

Chapter 5. Rvalue References, Move Semantics, and Perfect Forwarding

When you first learn about them, move semantics and perfect forwarding seem pretty straightforward:

Move semantics makes it possible for compilers to replace expensive copying operations with less expensive moves. In the same way that copy constructors and copy assignment operators give you control over what it means to copy objects, move constructors and move assignment operators offer control over the semantics of moving. Move semantics also enables the creation of move-only types, such as std::unique_ptr, std::future, and std::thread.
Perfect forwarding makes it possible to write function templates that take arbitrary arguments and forward them to other functions such that the target functions receive exactly the same arguments as were passed to the forwarding functions.

Rvalue references are the glue that ties these two rather disparate features together. They’re the underlying language mechanism that makes both move semantics and perfect forwarding possible.

The more experience you have with these features, the more you realize that your initial impression was based on only the metaphorical tip of the proverbial iceberg. The world of move semantics, perfect forwarding, and rvalue references is more nuanced than it appears. std::move doesn’t move anything, for example, and perfect forwarding is imperfect. Move operations aren’t always cheaper than copying; when they are, they’re not always as cheap ...