The difference between static_cast and dynamic_cast

In C, the difference between static_cast and dynamic_cast is: Security: static_cast is a static type conversion without runtime checking, which may lead to undefined behavior; dynamic_cast is a dynamic type conversion, which is checked at runtime to ensure The converted types are compatible and safer. Application scenarios: static_cast is used to convert compatible types and pointers/references; dynamic_cast is used to convert incompatible types and polymorphic scenarios. Result: static_cast always returns the value of the target type; dynamic_cast only returns the value of the target type when the conversion is successful, otherwise it returns nul

##static_cast and dynamic_cast The difference

static_cast and dynamic_cast are both operators used for type conversion, but there are significant differences between them .

1. Type safety

• static_cast is a static type conversion that is performed at compile time. Therefore, it does not perform any runtime checks and is therefore unsafe, possibly leading to undefined behavior.
• dynamic_cast is a dynamic type conversion that occurs at runtime. It performs a run-time check before performing the conversion to ensure that the target type is compatible with the source type. Therefore, it is much safer than static_cast.

2. Application scenarios

• static_cast Mainly used for:

  Convert compatible types, such as conversion between basic types.
  • Convert a pointer or reference, such as conversion from a base class pointer to a derived class pointer.

• dynamic_cast Mainly used for:

  Conversion of incompatible types, such as from base class pointer to derived class pointer Convert.
  • Perform type conversion in polymorphic scenarios, such as when you need to access a derived class object in a base class array.

3. Result

• static_cast always returns a value of the target type, even if The conversion was unsuccessful.
• dynamic_cast Returns a value of the target type only if the conversion is successful. If the conversion fails, nullptr is returned.

Example

<code class="cpp">// 实例化一个基类对象
Base* base = new Base();

// 使用 static_cast 转换基类指针到派生类指针
Derived* derived1 = static_cast<Derived*>(base); // 潜在的未定义行为

// 使用 dynamic_cast 转换基类指针到派生类指针
Derived* derived2 = dynamic_cast<Derived*>(base); // 返回 nullptr，因为 base 不是 Derived 类型的对象</code>

Conclusion

static_cast and dynamic_cast Has different roles and safety in type conversions. static_cast is used for fast, unsafe, compile-time conversions, while dynamic_cast is used for safe, run-time conversions. It is crucial to choose the appropriate operator based on the type and requirements of the conversion.

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