Heap or Stack: Where Does `new` Allocate Memory for C# Structs?

C# Structs and the 'new' Operator: Heap vs. Stack Allocation

The new operator with structs in C# introduces complexities regarding memory allocation (heap or stack). Unlike classes, which always allocate on the heap, structs exhibit nuanced behavior.

Parameterless Constructor Usage

Employing new with a parameterless constructor (e.g., new Guid()), allocates struct memory on the stack. The C# compiler treats this as a zero-initialization, not a constructor call, as per the CLI specification.

Constructors with Parameters

Using new with a parameterized constructor (e.g., new Guid(someString)) leads to context-dependent allocation:

• Temporary Values: When the struct serves as a temporary value (e.g., a method argument), the generated Intermediate Language (IL) allocates stack memory and executes the constructor.
• Variable or Field Assignment: Assigning to a local variable or field involves initial initobj allocation followed by the constructor call. Subsequent assignments using different constructors overwrite the existing data in the same memory location.
• Method Calls: Method calls utilize ldloca to obtain the variable's address. This cached address is then initialized using either initobj (parameterless constructors) or the constructor call (parameterized constructors), enabling memory reuse.

Summary

While conceptually, each new call on a struct might appear to allocate stack memory, the reality is more intricate. The allocation behavior depends heavily on the context. Understanding this nuance is critical for efficient code and preventing unforeseen complications.

The above is the detailed content of Heap or Stack: Where Does `new` Allocate Memory for C# Structs?. For more information, please follow other related articles on the PHP Chinese website!