When should I really use noexcept?

by

I think it is too early to give a “best practices” answer for this as there hasn’t been enough time to use it in practice. If this was asked about throw specifiers right after they came out then the answers would be very different to now.

Having to think about whether or not I need to append noexcept after every function declaration would greatly reduce programmer productivity (and frankly, would be a pain).

Well, then use it when it’s obvious that the function will never throw.

When can I realistically expect to observe a performance improvement after using noexcept? […] Personally, I care about noexcept because of the increased freedom provided to the compiler to safely apply certain kinds of optimizations.

It seems like the biggest optimization gains are from user optimizations, not compiler ones due to the possibility of checking noexcept and overloading on it. Most compilers follow a no-penalty-if-you-don’t-throw exception handling method, so I doubt it would change much (or anything) on the machine code level of your code, although perhaps reduce the binary size by removing the handling code.

Using noexcept in the big four (constructors, assignment, not destructors as they’re already noexcept) will likely cause the best improvements as noexcept checks are ‘common’ in template code such as in std containers. For instance, std::vector won’t use your class’s move unless it’s marked noexcept (or the compiler can deduce it otherwise).

More Related Contents:

  1. Difference between C++03 throw() specifier C++11 noexcept
  2. Why vector access operators are not specified as noexcept?
  3. Why doesn’t C++ use std::nested_exception to allow throwing from destructor?
  4. Is there an automatic noexcept specifier?
  5. What is the difference between C++03 `throw()` specifier and C++11 `noexcept`?
  6. `static constexpr` function called in a constant expression is…an error?
  7. C++ 11: conversion const int* to int* using unordered_set::push
  8. Undefined reference to static constexpr char[]
  9. Object destruction in C++
  10. Can’t pass temporary object as reference
  11. Is the size of std::array defined by standard
  12. constexpr and initialization of a static const void pointer with reinterpret cast, which compiler is right?
  13. std::map emplace without copying value
  14. When to use std::begin and std::end instead of container specific versions [duplicate]
  15. Garbage Collection in C++ — why?
  16. C++ Modules – why were they removed from C++0x? Will they be back later on?
  17. Which headers in the C++ standard library are guaranteed to include another header?
  18. Default template argument when using std::enable_if as templ. param.: why OK with two template functions that differ only in the enable_if parameter?
  19. How can an incomplete type be used as a template parameter to vector here?
  20. When Does Move Constructor get called?
  21. Questions about Hinnant’s stack allocator
  22. Equivalent of “using namespace X” for scoped enumerations?
  23. The implementation of random_device in VS2010?
  24. reinterpret_cast between char* and std::uint8_t* – safe?
  25. Check if a type is from a particular namespace
  26. How does =delete on destructor prevent stack allocation?
  27. Difference between a C++ exception and Structured Exception
  28. C++11 ‘native_handle’ is not a member of ‘std::this_thread’
  29. Does ‘auto’ type assignments of a pointer in c++11 require ‘*’?
  30. Why can’t C++11 move a noncopyable functor to a std::function?

Leave a Comment