Rud Merriam | A Journey into Non-Virtual Polymorphism 2 Who Doesn’t Recognize This?? 1990 Borland Turbo C++Cppcon 2023 | Rud Merriam | A Journey into Non-Virtual Polymorphism 3 Background ● Experience – Medium.com (https://medium.com/@rudmerriam)Cppcon 2023 | Rud Merriam | A Journey into Non-Virtual Polymorphism 4 Polymorphism ● Greek: “many forms” (Obligatory statement) ● The use of a single variableCppcon 2023 | Rud Merriam | A Journey into Non-Virtual Polymorphism 5 Polymorphic Variables ● Base class pointer to derived class – Virtual functions are not bad! ● Standard Template Library

carePhoto by Tech Nick on unsplashSimple benchmark class Base { public: int concrete() const; virtual int virt() const; }; void benchmark(Base *b, size_t num_iterations) { auto start = Clock::now(); virt_duration = end-start;There are interesting technical details and surprising conclusions that virtual functions can be actually faster. Since CPU architectures are mentioned, I'd expect to see deep nt-vs-inheritance-vs-other- ways-performanceDoes it even matter?Conclusions ● The notion that “virtual functions are slower” is flat out wrong. ○ Which is not to say they are faster ○ Some of the suggested

name, const NodeConfig& config) : SyncActionNode(name, config) {} // You must override this virtual function NodeStatus tick() override { std::cout << "Type: [ApproachEnemy]. Instance:" <<

Transactions of the block, only txid stored on kv, the detail information 33 // stored in another table 34 // 交易内容 35 repeated Transaction transactions = 11; 36 // The transaction count of the 转换后的c代码最终会编译成一个动态链接库来给XVM运行时来使用，在每个 生成的动态链接库里面都有如下初始化函数。 这个初始化函数会自动对wasm 里面的各个模块进行初始化，包括全局变量、内存、table、外部符号解析等。 1 typedef struct { 2 void* user_ctx; 3 wasm_rt_gas_t gas; 4 u32 g0; 5 t)); 11 (h->user_ctx) = user_ctx; 12 init_globals(h); 13 init_memory(h); 14 init_table(h); 15 return h; 16 } 3.4. 语言运行环境 3.4.1. c++运行环境 c++因为没有runtime，因此运行环境相对比较简单，只需要设置基础的堆栈分 布

of them are unique to Free Pascal. 88 Chapter 1 Reference for unit ’ascii85’ 1.1 Used units Table 1.1: Used units by unit ’ascii85’ Name Page Classes ?? System ?? sysutils ?? 1.2 Overview The ascThreeEncodedChars,ascFourEncodedChars, ascNoEncodedChar,ascPrefix) 89 CHAPTER 1. REFERENCE FOR UNIT ’ASCII85’ Table 1.2: Enumeration values for type TASCII85State Value Explanation ascFourEncodedChars Four encoded TASCII85RingBuffer.FillCount (95) 95 Chapter 2 Reference for unit ’AVL_Tree’ 2.1 Used units Table 2.1: Used units by unit ’AVL_Tree’ Name Page Classes ?? System ?? sysutils ?? 2.2 Overview The

In this document, data sizes are specified with pascal-style data types. They are the following: Table 1: Name Meaning longword Unsigned 32 bit integer. ptruint Unsigned integer of the size of a pointer also that pointers to strings are really pointers, and not offsets to the beginning of the string table. Resource sections Free Pascal uses two sections to store resource information: • fpc.resources in the form of nodes • The string table, which can be optional • The resource data The initial header The fpc.resources section starts with this header: Table 2: Name Offset Length Description

output_pin { public: virtual ~output_pin() = default; virtual void level(bool p_high) = 0; }; 2122 class output_pin { public: virtual ~output_pin() = default; virtual void level(bool p_high) not severe ‼ severe 🚨 28class output_pin { public: virtual ~output_pin() = default; virtual status level(bool p_high) = 0; virtual result level() = 0; }; 29 std::expected30 on GCC ARM 95Things that will NOT be covered here ● Nested exceptions ● Anything other than table based exceptions 96Consider the following 97 struct error {}; void foo() { try { bar();

. . . . 80 Normal static methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Virtual methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Abstract methods . 6.2 Invocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 6.6.3 Virtual methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 6.6.4 Class methods saveregisters softfloat specialize static stdcall stored strict unaligned unimplemented varargs virtual winapi write Remark Predefined types such as Byte, Boolean and constants such as maxint are not

included in the packages, or in the FCL. 139 Chapter 1 Reference for unit ’BaseUnix’ 1.1 Used units Table 1.1: Used units by unit ’BaseUnix’ Name Page unixtype 2087 1.2 Overview The BaseUnix unit was ESysENETUNREACH = 101 System error: Network is unreachable ESysENFILE = 23 System error: File table overflow ESysENOANO = 55 System error: No anode 146 CHAPTER 1. REFERENCE FOR UNIT ’BASEUNIX’ (User-defined signal 1) SIGUSR2 = 12 Signal: USR2 (User-defined signal 2) SIGVTALRM = 26 Signal: VTALRM (Virtual alarm clock) SIGWINCH = 28 Signal: WINCH (Window/Terminal size change) SIGXCPU = 24 Signal: XCPU

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 6.10.3 The ASCII table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 6.10.4 The calculator . . . . or /lib/ld- linux.so.1, depending on which one is found first. -Fmxxx Load the unicode conversion table from file x.txt in the directory where the compiler is located. Only used when -Fc is also in effect run-time error will be generated. -CR Generate checks when calling methods to verify if the virtual method table for that object is valid. -Csxxx Set stack size to xxx. -Ct Generate stack checking code