---
id: wiki-2026-0508-vfunction
title: vFunction
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [virtual function, 가상 함수, vFunction.com]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [oop, polymorphism, architecture, modernization]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: cpp
  framework: none
---

# vFunction

## 매 한 줄
> **"매 dispatch 의 runtime 의 resolve"**. 매 term 의 two meanings — (1) C++ `virtual` function (vtable-based dynamic dispatch), (2) vFunction.com (AI-driven Java monolith → microservices modernization platform). 매 context 의 disambiguate.

## 매 핵심

### 매 (1) Virtual function (C++)
- **vtable**: 매 class per — function pointer table.
- **vptr**: 매 instance per — vtable 의 pointer.
- **Dispatch**: `obj->fn()` → `obj->vptr[fn_index]()` (one extra indirection).
- **Cost**: ~1-2 ns per call, 매 inlining 의 block.
- **Override**: derived class 의 same signature 의 redefine.

### 매 (2) vFunction.com platform
- **Static + dynamic analysis**: 매 Java/.NET monolith 의 scan.
- **Domain extraction**: AI 의 bounded context 의 cluster.
- **Refactor recommendation**: 매 service boundary + dead code + TCO.
- **2025 update**: Claude/GPT-5 backed reasoning, 매 Spring Boot extraction template.

### 매 응용 (vfunc C++)
1. Strategy pattern.
2. Plugin/driver interface.
3. Mock injection 의 testing.

### 매 응용 (vFunction.com)
1. Legacy Java EE → microservice migration.
2. Technical debt quantification.
3. Architectural drift detection.

## 💻 패턴

### Virtual function (modern C++20)
```cpp
struct Shape {
    virtual ~Shape() = default;
    virtual double area() const = 0;       // pure virtual
};

struct Circle : Shape {
    double r;
    explicit Circle(double r) : r(r) {}
    double area() const override { return 3.14159 * r * r; }
};

double total(std::span<const std::unique_ptr<Shape>> shapes) {
    double s = 0;
    for (auto& sh : shapes) s += sh->area();   // dynamic dispatch
    return s;
}
```

### Devirtualization hint (final)
```cpp
struct FastCircle final : Shape {              // final → compiler 의 devirtualize
    double area() const override final { return 3.14; }
};
```

### CRTP (static polymorphism, vfunc 의 X)
```cpp
template<class Derived>
struct Shape {
    double area() const { return static_cast<const Derived*>(this)->area_impl(); }
};

struct Square : Shape<Square> {
    double s;
    double area_impl() const { return s * s; }   // zero overhead
};
```

### Rust (trait object, vfunc analog)
```rust
trait Shape { fn area(&self) -> f64; }
struct Circle { r: f64 }
impl Shape for Circle { fn area(&self) -> f64 { 3.14 * self.r * self.r } }

fn total(shapes: &[Box<dyn Shape>]) -> f64 {
    shapes.iter().map(|s| s.area()).sum()  // dyn dispatch via vtable
}
```

### vFunction.com workflow (concept)
```yaml
# .vfunction/config.yaml
target: java/spring-boot
analyze:
  paths: [src/main/java]
  exclude: [test, generated]
extract:
  strategy: domain-driven
  min-cohesion: 0.7
recommendations:
  - service-boundaries
  - dead-code
  - dependency-cycles
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Runtime polymorphism, OOP | virtual function |
| Hot loop, type known | CRTP / template |
| Plugin boundary | virtual + dyn lib |
| Legacy Java refactor | vFunction.com |
| Greenfield modular | DDD + bounded context |

**기본값**: virtual function 의 default OOP, CRTP 의 perf-critical.

## 🔗 Graph
- 부모: [[Object-Oriented-Programming]] · [[Polymorphism]]
- 변형: [[CRTP]] · [[Trait Objects]] · [[Function Pointers]]
- 응용: [[Strategy Pattern]] · [[Plugin Architecture]] · [[Microservices Migration]]
- Adjacent: [[Inheritance]] · [[Dynamic Dispatch]] · [[Legacy Modernization]]

## 🤖 LLM 활용
**언제**: legacy code 의 virtual function chain 의 analyze, 매 modernization scope 의 estimate.
**언제 X**: 매 micro-optimization decision (devirtualize 의 X) — 매 profiler 의 use.

## ❌ 안티패턴
- **Virtual everything**: 매 every method 의 virtual, 의 cost + 의 hard 의 reason. Final 의 default.
- **Diamond inheritance**: 매 multiple virtual base, 의 composition 의 prefer.
- **Virtual destructor 의 forget**: base class polymorphic, 의 leak.
- **vFunction 의 silver bullet**: tool 의 recommendation 의 blindly 의 apply, 의 domain understanding 의 first.

## 🧪 검증 / 중복
- Verified (ISO C++ standard, Stroustrup "Tour of C++" 3rd, vfunction.com docs 2025).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full vFunction (virtual + platform) entry |
