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add reference to RTTI

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Bjarne Stroustrup
2015-10-09 17:51:40 -04:00
parent 72821c0f88
commit 70a19387fe
1 changed files with 5 additions and 1 deletions
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CppCoreGuidelines.md
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@@ -5681,7 +5681,7 @@ Consider:
The result of `pb2=="D"` is actually implementation defined. The result of `pb2=="D"` is actually implementation defined.
We added it to warn of the dangers of home-brew RTTI. We added it to warn of the dangers of home-brew RTTI.
This code may work as expected for years, just to fail on a new machine or new compiler that does not unify character literals. This code may work as expected for years, just to fail on a new machine, new compiler, or a new linker that does not unify character literals.
If you implement your own RTTI, be careful. If you implement your own RTTI, be careful.
@@ -5693,6 +5693,10 @@ You will basically be crafting your own special-purpose `dynamic_cast`.
So, first make sure that your `dynamic_cast` really is as slow as you think it is (there are a fair number of unsupported rumors about) So, first make sure that your `dynamic_cast` really is as slow as you think it is (there are a fair number of unsupported rumors about)
and that your use of `dynamic_cast` is really performance critical. and that your use of `dynamic_cast` is really performance critical.
We are of the opinion that current implementations of `dynamic_cast` are unnecessarily slow.
For example, under sutitable conditions, it is possible to perform a `dynamic_cast` in [fast constant time](http://www.stroustrup.com/fast_dynamic_casting.pdf).
However, compatibility makes changes difficult even if all agree that an effort to optimize is worth while.
##### Enforcement ##### Enforcement
Flag all uses of `static_cast` for downcasts, including C-style casts that perform a `static_cast`. Flag all uses of `static_cast` for downcasts, including C-style casts that perform a `static_cast`.