## +23 ## Undefined Behavior: What Every Programmer Should Know and Fear ## FEDOR PIKUS ## 20 23 October 01 - 06 ## We will learn: ## • What is Undefined Behavior - And what it is not UB vs implementation-defined programs? ## What is Undefined Behavior (UB) in C++? • The concept is defined in the standard int f(int k) { • According to the standard, if k > INT_MAX-10, the result is undefined – “The program is - True danger of UB: the result of the entire program is undefined if any operation exhibits UB (according to the standard) • "Undefined" means the standard imposes no requirements on such result

## 可觀測性 (Observability) 在 Kubernetes Day2 Operation的考量與實踐 E.W. Kuo @ iThome Kubernetes Summit 2022 ## 二 哥 • 緯創資通員工 • 社群的參與者 技術的佈道師 • 台灣資料工程協會會員 • Kafka 修煉之道講師 Wistron DX lab 緯創數位轉型技術實驗室  Day2 Operation Challenge of Kubernetes Day 2 Operation ![Image](/uploads/documents/0/4/3/7/043796e15ae22f838e151dd5ff3589e7/p3_2 可觀測性 關聯演示 ## Day2 Operation 定義與說明 ## Day 2 Operation 的定義 - 一旦“某物”投入運營，Day 2 Operation 就是直到該“某物”被移除或被取代前所需要照料它的時間段。 - Day 2 Operation 是系統為組織生成結果與價值的地方。 - 組織需要在 Day 2 Operation 中不斷尋求改進，以最大限度地提高收益。

safe This is  ## Undefined Behavior! This is  initialized int a; // not initialized int b{a}; // ?? int a; // not initialized int b{a}; // undefined behavior auto double_in_place(int& v) { v *= 2; } Elementary Form: Programming Compiler jpg) This is  ## Undefined Behavior! Is C++ safe? Modern C++: # Effective reference syntax Modern C++ 42 SPECIFIC WAYS TO

sql queries in the beeline console. For instance, > SHOW DATABASES; You will see a wall of operation logs, and a result table in the beeline console. omitted logs |\| namespace \|| |---| |\| default by Apache Hive 0: jdbc:hive2://localhost:10009/> show databases; 2020-11-16 23:50:50.388 INFO operation.ExecuteStatement: Spark application name: kyuubi_kentyao_spark_2020-11- 16T15:50:08.968Z application HiveMetaStore.audit: ugi=kentyao ip=unknown-ip-addr cmd=get_databases: * 2020-11-16 23:50:50.423 INFO operation.ExecuteStatement: Processing kentyao's query[8453e657-c1c4-4391-8406-ab4747a66c45]: RUNNING_STATE

sql queries in the beeline console. For instance, > SHOW DATABASES; You will see a wall of operation logs, and a result table in the beeline console. omitted logs |\| namespace \|| |---| |\| default by Apache Hive 0: jdbc:hive2://localhost:10009/> show databases; 2020-11-16 23:50:50.388 INFO operation.ExecuteStatement: Spark application name: kyuubi_kentyao_spark_2020-11- 16T15:50:08.968Z application HiveMetaStore.audit: ugi=kentyao ip=unknown-ip-addr cmd=get_databases: * 2020-11-16 23:50:50.423 INFO operation.ExecuteStatement: Processing kentyao's query[8453e657-c1c4-4391-8406-ab4747a66c45]: RUNNING_STATE

sql queries in the beeline console. For instance, > SHOW DATABASES; You will see a wall of operation logs, and a result table in the beeline console. omitted logs |\| namespace \|| |---| |\| default by Apache Hive 0: jdbc:hive2://localhost:10009/> show databases; 2020-11-16 23:50:50.388 INFO operation.ExecuteStatement: Spark application name: kyuubi_kentyao_spark_2020-11- 16T15:50:08.968Z application HiveMetaStore.audit: ugi=kentyao ip=unknown-ip-addr cmd=get_databases: * 2020-11-16 23:50:50.423 INFO operation.ExecuteStatement: Processing kentyao's query[8453e657-c1c4-4391-8406-ab4747a66c45]: RUNNING_STATE

jdbc:hive2://10.242.189.214:2181/> select timestamp '2018-11-17'; 2021-10-28 13:56:27.509 INFO operation.ExecuteStatement: Processing kent's query[1f619182-20ad-4733-995b-a5e43b80d998]: INITIALIZED_STATE -> PENDING_STATE, statement: select timestamp '2018-11-17' 2021-10-28 13:56:27.547 INFO operation.ExecuteStatement: Processing kent's query[1f619182-20ad-4733-995b-a5e43b80d998]: PENDING_STATE -> RUNNING_STATE, statement: select timestamp '2018-11-17' 2021-10-28 13:56:27.540 INFO operation.ExecuteStatement: Processing kent's query[a46ca504-fe3a-4dfb-be1e-19770af8ac4c]: INITIALIZED_STATE

jdbc:hive2://10.242.189.214:2181/> select timestamp '2018-11-17'; 2021-10-28 13:56:27.509 INFO operation.ExecuteStatement: Processing kent's query[1f619182-20ad-4733-995b-a5e43b80d998]: INITIALIZED_STATE -> PENDING_STATE, statement: select timestamp '2018-11-17' 2021-10-28 13:56:27.547 INFO operation.ExecuteStatement: Processing kent's query[1f619182-20ad-4733-995b-a5e43b80d998]: PENDING_STATE -> RUNNING_STATE, statement: select timestamp '2018-11-17' 2021-10-28 13:56:27.540 INFO operation.ExecuteStatement: Processing kent's query[a46ca504-fe3a-4dfb-be1e-19770af8ac4c]: INITIALIZED_STATE

jdbc:hive2://10.242.189.214:2181/> select timestamp '2018-11-17'; 2021-10-28 13:56:27.509 INFO operation.ExecuteStatement: Processing kent's query[1f619182-20ad-4733-995b-a5e43b80d998]: INITIALIZED_STATE -> PENDING_STATE, statement: select timestamp '2018-11-17' 2021-10-28 13:56:27.547 INFO operation.ExecuteStatement: Processing kent's query[1f619182-20ad-4733-995b-a5e43b80d998]: PENDING_STATE -> RUNNING_STATE, statement: select timestamp '2018-11-17' 2021-10-28 13:56:27.540 INFO operation.ExecuteStatement: Processing kent's query[a46ca504-fe3a-4dfb-be1e-19770af8ac4c]: INITIALIZED_STATE

includes such issues as the nature of programming environments and the error messages returned for undefined programs (i.e. programs that formally evaluate to $ \bot $ ). ### 1.1 Program Structure In this user. The Prelude provides two functions to directly cause such errors: error :: String -> a undefined :: a A call to error terminates execution of the program and returns an appropriate error indication in some system-dependent manner. When undefined is used, the error message is created by the compiler. Translations of Haskell expressions use error and undefined to explicitly indicate where execution