Difference between revisions of "Intermediate C++ Game Programming Tutorial 22"
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** You can enable move operations in these cases by making the move constructor <code>noexcept</code>, which explicitly tells the compiler that there will be no exception thrown | ** You can enable move operations in these cases by making the move constructor <code>noexcept</code>, which explicitly tells the compiler that there will be no exception thrown | ||
** Be mindful of when you mark your functions noexcept. You basically enter into a contract with whomever is using your code that the function will never throw exceptions. If you would ever want to change this, you risk nasty errors because the codebase may rely on your function being <code>noexcept</code>. | ** Be mindful of when you mark your functions noexcept. You basically enter into a contract with whomever is using your code that the function will never throw exceptions. If you would ever want to change this, you risk nasty errors because the codebase may rely on your function being <code>noexcept</code>. | ||
| + | * Best practices [https://youtu.be/DMdyz0lrFBI?t=21m56s 21:56] | ||
</div> | </div> | ||
[https://youtu.be/_6G5yDgoWiA Tutorial 22 Part 2] | [https://youtu.be/_6G5yDgoWiA Tutorial 22 Part 2] | ||
Revision as of 06:25, 24 November 2019
In this video we learn how to use C++ exceptions to take our error handling to the next level. There is a lot of fear and ignorance surrounding exceptions among "C++ Programmers", and Chili's goal here is to elevate you guys above the shit-tier level to coders who can actually use this feature to its full extent. The second part of this tutorial will give concrete, practical examples of using exceptions in an actual game scenario.
Topics Covered
- Basic exception
tryingthrowing andcatching - Exceptions 'bubbling up'
- Rethrowing with
throw -
std::exceptionand its derivatives - Polymorphism in exception handling
-
catch(...) - Throw by value, catch by
constreference - Exceptions and destructors
-
noexceptand move constuctors vs. standard containers
Video Timestamp Index
- Intro: exceptions are the main way of handling errors in C++ 0:10
- Examples of its usage in the Framework, a good practice for working with any API
- Everytime a Direct 3D Function is called, the return value is checked for error codes and handled
- Comparing error handling with and without exceptions 1:40
- Conventional error handling requires checking function return errors for every function throughout the entire hierarchy of the code base
- With exceptioins the advantages are:
- - you can catch an error anywhere in the code base (they "bubble up", or propagate up to a higher level function)
- - you can seperate your normal logic (code) from your error handling, without having to pollute your return values with error codes.
- - if you don't handle the error at some point, your program will be halted (uncaught exception).
- Example code to demonstrate
try,throw,catchof astd::runtime_error("...")3:53
- The
catchfunction is only executed if an exception has been thrown - Illustration of how exceptions can propagate out of functions
- You can decide the level at which you want to catch an exception 6:04
- Catch and rethrow 6:40
- You can
throwanything you want: an object, an Integer, string, pointer, etc. - You van overload the
catchfunctions based on the type of information thrown
- The
- Use
catch(...)to catch any uncaught excepions 8:55- In this case, you don't get any exception object or value that you can output
- Rethrowing still works
- Good practice: only throw exception objects that inherit from the
std::exceptionclass 9:51- STL offers a range of pre-defined exception objects, with two basic types that inherit from
std::exception:
- -
std::logic_error: due to faulty logic within the program - -
std::runtime_error: due to events beyond the scope of the program (such as file access errors)
- STL offers a range of pre-defined exception objects, with two basic types that inherit from
- The inherentance hierarchy of
std::exceptionis very useful 10:49- The polymorphism lets you choose the level of detail in error handling, so that you can filter for specific errors
- You can use parent types to catch general exceptions
- An exception will be caught (/dispatched) to its most derived (most specific) type, when catch functions are overloaded for different types of exceptions
- You can create your own error classes that inherit from the existing one for customized and finer-grained error handling
- Exceptions and destructors 13:39
- If you throw an exception, the code is going to jump out of the current function to wherever it is being caught
- Upon jumping out of scope, all objects in scope will be destroyed. This is called "unwinding the stack"
- However, any objects created on the heap will not be destroyed, resulting in a memory leak
- This is avoided by using unique (smart) pointers and allocate memory with
std::make_unique<>()instead of using raw pointers andnew - More generally, if you use RAII types (such as
std::vector<>,std::stringetc.), you will have no issues with memory leaks
- Pitfalls 17:17
- Never have destructors throw exceptioins, this will mess up execution bigly
- If you call any functions that can throw exceptions in a destructor, make sure you always catch them
- Move semantics and containers 18:34
- Move operations don't work well if an exception is thrown
- If a move constructor of a class can throw an exception, the STL classes will avoid it and default to the copy constructor
- You can enable move operations in these cases by making the move constructor
noexcept, which explicitly tells the compiler that there will be no exception thrown - Be mindful of when you mark your functions noexcept. You basically enter into a contract with whomever is using your code that the function will never throw exceptions. If you would ever want to change this, you risk nasty errors because the codebase may rely on your function being
noexcept.
- Best practices 21:56
Extra Discussion
I had an interesting exchange with a viewer, and made a bit of a writeup here: essay time.
