如何在 C++ 中将无符号长整型 (DWORD) 重新解释为有符号长整型？
我想将 unsigned long （实际上是 DWORD）重新解释为 signed long。我尝试过：
DWORD x;
long y = reinterpret_cast<signed long>(x);
但是，VC++2010智能感知告诉我“无效的类型转换”。为什么？我该如何修复它？
I want to reinterpret an unsigned long (actually, a DWORD) as a signed long. I tried:
DWORD x;
long y = reinterpret_cast<signed long>(x);
However, VC++2010 intellisense tells me "Invalid type conversion". Why? How do I fix it?
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您不需要
reinterpret_cast将无符号类型转换为有符号类型，static_cast即可。You don't need
reinterpret_castto convert unsigned type into a signed one,static_castwill do.尝试使用 static_cast 代替。如果您尝试过度宽松的强制转换（例如当 static_cast 或 const_cast 就足够时使用reinterpret_cast），VC 会生成错误。
C++ 中有 5 种类型的强制转换，每种类型都允许您执行更多操作（授予更多权限）。最少允许的强制转换是 const 强制转换 (
const_cast() )，它允许您更改 const 修饰符。有静态转换 (static_cast)() )，允许您执行类型安全的强制转换（例如，将基类转换为派生类）。还有动态转换 (动态_cast<衍生类型>(base_type)允许您从一种类型转换为另一种类型，如果两者之间存在合法转换（如果没有合法转换，则返回 null最后，还有一些类型转换允许在不相关的类型之间进行转换——reinterpret_castreinterpret_cast() 和 C 风格类型转换(int)操作 我没有一个好的方法来描述这些不同类型的强制转换，因此我将它们描述为“更宽松”，因为它们中的每一个都允许您执行更多
。当其他强制转换类型之一更适合实现您的目标时，重新解释强制转换。 C 样式强制转换没有类似的向后兼容性警告。
try static_cast instead. VC generates an error if you try an excessively permissive cast (like using reinterpret_cast when static_cast or const_cast will suffice).
There are 5 types of casts in C++, each of which allows you to do more (grants more permissions). The least permissive casts are const casts (
const_cast<int>(<const int>)) which allow you to change the const modifier. There are static casts (static_cast<int>)(<short>)) which allow you to perform type safe coersions (cast base to derived, for example).There are dynamic casts (dynamic_cast<derived_type>(base_type)that allow you to cast from one type to another if there is a legal conversion between the two (and that return null if there is no conversion). Finally, there are casts that allow conversion between unrelated types - reinterpret_castreinterpret_cast<int>(<void *>)and C style cast(int)<void *>.I don't have a good way of describing these different types of casts, so I describe them as "more permissive" because each of them allows you to do more.
VC warns you if you are using a reinterpret cast when one of the other cast types would be more appropriate to achieve your goal. C style casts don't have a similar warning for backwards compatibility.