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Fix C.183.

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Gabriel Dos Reis
2017-05-01 11:05:32 -07:00
parent 918a5695c7
commit f9f3422ac5
1 changed files with 4 additions and 2 deletions
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CppCoreGuidelines.md
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@@ -8024,11 +8024,11 @@ If you wanted to see the bytes of an `int`, use a (named) cast:
void if_you_must_pun(int& x) void if_you_must_pun(int& x)
{ {
auto p = reinterpret_cast<unsigned char*>(&x); auto p = reinterpret_cast<unsigned char*>(&x);
cout << p[0] << '\n'; // undefined behavior cout << p[0] << '\n'; // OK; better
// ... // ...
} }
Accessing the result of an `reinterpret_cast` to a different type from the objects declared type is still undefined behavior, Accessing the result of an `reinterpret_cast` to a different type from the objects declared type is defined behavior (even though `reinterpret_cast` is discouraged),
but at least we can see that something tricky is going on. but at least we can see that something tricky is going on.
##### Note ##### Note
@@ -8036,6 +8036,8 @@ but at least we can see that something tricky is going on.
Unfortunately, `union`s are commonly used for type punning. Unfortunately, `union`s are commonly used for type punning.
We don't consider "sometimes, it works as expected" a strong argument. We don't consider "sometimes, it works as expected" a strong argument.
C++17 introduced a distinct type `std::byte` to facilitate operations on raw object representation. Use that type instead of `unsigned char` or `char` for these operations.
##### Enforcement ##### Enforcement
??? ???