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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 ✅
