第一部分： 目的是什麼？Checked delete 慣用法增加了編譯時安全檢查，防止刪除不完整類。C++ 標準規定，指向不完整類的指標可以被刪除，前提是該類具有
平凡解構函式且
沒有過載 operator delete。刪除指向具有非平凡解構函式或過載 operator delete 的類的指標會導致
未定義行為。
第二部分： 有問題程式碼示例考慮以下程式碼
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/* Deleter.hpp */
#include<cstdlib>
class A;
class B;
class C;
void func1(A* a);
void func2(B* b);
void func3(C* c);
/* End of Deleter.hpp */
/* Deleter.cpp */
#include "Deleter.hpp"
void func1(A* a)
{
delete a;
}
void func2(B* b)
{
delete b;
}
void func3(C* c)
{
delete c;
}
/* End of Deleter.cpp */
/* Classes.hpp */
class A
{
private:
int* x;
public:
A(void)
{
x = new int(4);
}
~A(void)
{
delete x;
}
};
class B { };
class C
{
public:
void operator delete(void* pointer)
{
free(pointer);
}
};
/* End of Classes.hpp */
/* Main.cpp */
#include "Deleter.hpp"
#include "Classes.hpp"
int main(void)
{
A* a = new A;
func1(a); // <-- Undefined Behavior - A has a non-trivial destructor
B* b = new B;
func2(b); // <-- Legal - B has a trivial destructor and does not overload operator delete
C* c = new C;
func3(c); // <-- Undefined Behavior - C has an overloaded operator delete
return 0;
}
/* End of Main.cpp */
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大多數編譯器會為此類情況生成警告，但據報道有些編譯器不會捕獲這些錯誤。這就是 checked delete 慣用法旨在解決的問題。
第三部分： 逐行解析原始原始碼列在本文章的頂部。
以下程式碼已移除註釋和預處理器指令。
Boost 對 checked delete 慣用法的實現包括兩個函式模板和兩個類模板。
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template<class T> void checked_delete(T* p)
{
typedef char type_must_be_complete[ sizeof(T)? 1: -1 ];
(void) sizeof(type_must_be_complete);
delete p;
}
template<class T> struct checked_deleter
{
typedef void result_type;
typedef T * argument_type;
void operator()(T * x) const
{
boost::checked_delete(x);
}
};
template<class T> void checked_array_delete(T* p)
{
typedef char type_must_be_complete[ sizeof(T)? 1: -1 ];
(void) sizeof(type_must_be_complete);
delete [] p;
}
template<class T> struct checked_array_deleter
{
typedef void result_type;
typedef T * argument_type;
void operator()(T * x) const
{
boost::checked_array_delete(x);
}
};
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雖然程式碼的主體看起來非常相似，但其中一組用於檢查
operator delete，另一組用於檢查
operator delete[]。
警告 - 以下內容包含無法從 Boost 文件引用的觀點。
第 1-6 行
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template<class T> void checked_delete(T* p)
{
typedef char type_must_be_complete[ sizeof(T)? 1: -1 ];
(void) sizeof(type_must_be_complete);
delete p;
}
// Line 3:
// sizeof(T) will either evaluate to 0,
// or cause a compiler error if T is an incomplete type.
// If sizeof(T) evaluates to 0, then a compiler error is
// caused by attempting to declare an array of -1 elements.
//
// Line 4: * Citation Needed
// While I cannot be sure of why line 4 is there,
// I assume that it is to prevent the compiler from
// complaining about an unused variable, while at the
// same time helping it optimize the build casting the
// result of sizeof(type_must_be_completed) to void.
//
// Line 5:
// operator delete is called on the parameter
//
// Furthermore, it can be deduced that the defined
// type, `type_must_be_complete`, is named as such
// to aid in the debugging process, as it will show
// up in the compiler output as an indicator of where
// the problem lies.
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第 8-16 行
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template<class T> struct checked_deleter
{
typedef void result_type;
typedef T * argument_type;
void operator()(T * x) const
{
boost::checked_delete(x);
}
};
// Lines 3 & 4:
// As far as I can see, lines 3 and 4 are present
// for documentation purposes.
// Lines 5-8:
// The overloaded operator() simply calls the corresponding
// function.
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第 19-34 行
checked_array_delete 的逐行解析與上述基本相同。 
