Proper Design Pattern — Key to Safety in C++

Listen to this Post

Featured Image
Design patterns are crucial in software development to ensure safety, maintainability, and scalability. One common issue in C++ is handling null pointers, which can lead to undefined behavior if not managed properly. This article explores the Proxy Pattern as a solution to eliminate scattered null checks and improve code robustness.

🔗 Compiler Explorer Example (Original Fragile Design):

👉 https://godbolt.org/z/57aMx7KsE

🔗 Updated Example (Proxy Pattern Solution):

👉 https://godbolt.org/z/hazzW4Pqc

You Should Know:

Key Concepts & Implementation

1. The Problem: Fragile Null Checks

When a class (Bar) stores a std::unique_ptr<Foo>, it must check for null before dereferencing. This leads to:
– Scattered validation logic (redundant checks).
– Risk of missed checks during refactoring.
– Undefined behavior if a null pointer is dereferenced.

2. The Solution: Proxy Pattern

Instead of exposing raw pointers, we use:

– `IBar` (abstract interface).
– `BaseBar` (implements core logic without Foo).
– `ProxyBar` (delegates to `Foo` only when valid).

3. Benefits

✅ No accidental null dereferencing (compile-time safety).

✅ Clean separation of concerns (logic with/without `Foo`).

✅ Easier maintenance (no scattered null checks).

Practical Implementation (Code Snippets)

Original Fragile Design

class Bar {
std::unique_ptr<Foo> m_foo;
public:
void doWork() {
if (m_foo) { // Must check every time!
m_foo->execute();
}
}
};

Proxy Pattern Solution

class IBar {
public:
virtual void doWork() = 0;
virtual ~IBar() = default;
};

class BaseBar : public IBar {
public:
void doWork() override { / Work without Foo / }
};

class ProxyBar : public IBar {
std::unique_ptr<Foo> m_foo;
public:
void doWork() override {
m_foo->execute(); // Safe, Foo is guaranteed valid
}
};

Factory Function (`makeBar`)

std::unique_ptr<IBar> makeBar(bool needsFoo) {
if (needsFoo) {
return std::make_unique<ProxyBar>(std::make_unique<Foo>());
}
return std::make_unique<BaseBar>();
}

Linux & Windows Commands for Debugging C++

Linux (GDB)

g++ -g -o program main.cpp  Compile with debug symbols 
gdb ./program  Start debugger 
break Bar::doWork  Set breakpoint 
run  Execute 
info locals  Inspect variables 

Windows (WinDbg)

cl /Zi main.cpp  Compile with debug info 
windbg program.exe  Launch debugger 
bp program!Bar::doWork  Set breakpoint 
g  Run 
dv /i  View variables 

Valgrind (Memory Leak Checker)

valgrind --leak-check=full ./program 

What Undercode Say

The Proxy Pattern is a powerful tool to enforce null safety in C++. By abstracting pointer handling, we reduce bugs and improve maintainability.

🔹 Key Takeaways:

  • Avoid raw pointer exposure (use interfaces).
  • Leverage smart pointers (std::unique_ptr, std::shared_ptr).
  • Debug early (GDB, WinDbg, Valgrind).

🔹 Future-Proofing:

  • Static analyzers (clang-tidy, cppcheck) can catch null-deref issues.
  • Unit testing (Google Test) ensures proxy behavior.

Expected Output:

A safer, more maintainable C++ codebase with:

✔ No accidental null dereferences.

✔ Cleaner architecture.

✔ Easier debugging.

🔗 Further Reading:

Prediction

As C++ evolves, compile-time null-safety (like Rust’s Option) may become standard. Until then, Proxy Pattern remains a robust solution. 🚀

IT/Security Reporter URL:

Reported By: Nikolai Kutiavin – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

Join Our Cyber World:

💬 Whatsapp | 💬 Telegram