into instructions. ## • Globals: - Unsafe for multiple threads • Limited. • Exceptions: • Size: RTTI information, catch tables, landing pad assembly, etc. • Runtime: Load cold code from memory, dynamic Table based implementation of exceptions will add the following functionality to the program: 1. RTTI will be generated in order to identify the exception type. 2. Exception handlers will be defined minimal data needed. 4. Uniform exception (single type) or use static type: minimizing catch data + RTTI. ## PART IV: ALTERNATIVES Other suggestions for error handling are on the table as well: 1. Contracts

prevent code duplication for member functions ## Run Time Type Information (RTTI) 1. Extra information stored for each polymorphic type in an implementation defined struct 2. Allows Allows for querying type information at run time 3. Can be disabled to save space (gcc/clang -fno-rtti, msvc /GR-) ## dynamic_cast struct A { virtual ~A() = default; }; struct B : public A { }; struct Can only be a reference or pointer 3. Cannot remove CV 4. From must be polymorphic 5. Requires RTTI ### 6. Returns nullptr for pointers and throws std::bad_cast for references if the types are not

Memory Usage Increases Binary Size Requires whole C++ STL Exception Tables Run Time Type Info (RTTI) Exception Code TIME Nondeterministic Type Comparison (dynamic\_cast)  Exception Code TIME Nondeterministic Type Comparison (dynamic_cast) 🙏 😄 ## Slow Binary Spectre of RTTI ## Breaking Barrier #4 Disabling RTTI ## Breaking Barrier #4: Disabling RTTI ## Action: Replace -frtti with -fno-rtti What happens if you disable it? Note: C++ Exceptions REQUIRE RTTI to work

rule (no pun intended) for Windows code. ## Run-Time Type Information (RTTI) Avoid using Run Time Type Information (RTTI). RTTI allows a programmer to query the C++ class of an object at run time. This runtime is often an indication that the design of your class hierarchy is flawed. Undisciplined use of RTTI makes code hard to maintain. It can lead to type-based decision trees or switch statements scattered the code, all of which must be examined when making further changes. The standard alternatives to RTTI (described below) require modification or redesign of the class hierarchy in question. Sometimes such

objects” at runtime. • Despite the temptation, we must do compile time RTTI, anyone? • We can lean on consteval to avoid RTTI! A new hope! P2996 

的程序代码，我所据以解说的，是大众化选项下的产品。 第四篇以微软公司附于Visual C++ 光盘片上的一个范例程序Scribble 为主轴，一步一步加 上新的功能。并在其间深入介绍Runtime Type Information（RTTI）、Dynamic Creation、 Persistence（Serialization）、Message Mapping、Command Routing 等核心技术。这些技术正 是其它书籍最缺 C++ 程式的生與死：兼談建構式與解構式 / 088 * ㆕種不同的物件生存方式 / 090 * 所謂 "Unwinding" / 092 執行時期型別資訊（RTTI） / 092 動態生成（Dynamic Creation） / 095 異常處理（Exception Handling） / 096 Template 111 Frame1 範例程式 / 111 MFC 程式的初始化過程 / 115 Frame2 範例程式 / 118 RTTI（執行時期型別辨識） / 122 CRuntimeClass 與類別型錄網 / 123 DECLARE_DYNAMIC / IMPLEMENT_DYNAMIC

over current techniques • Modules • Patterns and Tricks for runtime reflection ## I mplementing an RTTI runtime • Go from client API json sanitize_struct(any any_value) { json json; for (Field value(); json[f.name]["type"] = f.type; } return json; } ## I mplementing an RTTI runtime om realistic client API struct AnyRef { void* value; const Type* type; }; json s value(any_value); json[f.name]["type"] = f.type; } return json; } ## I mplementing an RTTI runtime Gathering type data → Type registry: Contains type definitions → Public API: .type->fields

the compiler will generate Run-Time Type Information (RTTI). All descendent class of a class that was compiled in the $ \{SM+\} $ state will get RTTI information too. Any class that is used as a field or or property in a published section will also get RTTI information. By default, no Run-Time Type Information is generated for published sections, making them equivalent to public sections. Only when a (or one of its parent classes) was compiled in the $ \{SM+\} $ state, the compiler will generate RTTI for the methods and properties in the published section. The TPersistent object that is present in

three consequences of having different types: 1. That they have different typeinfo, hence different RTTI (Run-Time Type Information). 2. They can be used in function overloads, that is Procedure MyProc(A that in an instance, the fields do not necessarily appear in the same order as in the declaration. RTTI generated for a class will reflect this change. #### 6.3.2 Class fields/variables Similar to objects published section. For methods, fields and properties in the Published section, the compiler generates RTTI information (Run Time Type Information), which can be used to query the defined methods, fields and

switch. Possible values are: HEAP Allow heap memory. INITFINAL Initialization/finalization. RTTI Allow use of RTTI. CLASSES Allow use of classes. EXCEPTIONS Allow use of exceptions. EXITCODE Allow use this could create problems if two differently cased versions of the same filename are in the path. - RTTI is NOT stored in the same way as for Delphi. The format is mostly compatible, but may differ. This This should not be a problem if the API of the TypeInfo unit is used and no direct access to the RTTI information is attempted. • By default, sets are of different size than in Delphi, but set size can be