C/C++ Programming (2021-12-06 - 2021-12-10, 2022-01-24 - 2022-02-04)

Contents

Material

• Course Description

• Slide Material

Git

• Please create GitHub account

• Create access token

• Clone our repository (jfasch/2021-12-06):

  $ git clone https://github.com/jfasch/2021-12-06
  

2021-12-06

• Installation

• Introduction

• Hello World

• Variables and Arithmetic

• Pointers, Arrays, and Commandline

  

• Exercise: A Better Fahrenheit Table

• for Loops

• Exercise: Fahrenheit Table Using for

  Solutions:

  • fahrenheit-for.c

  • fahrenheit-for-reverse.c

  • fahrenheit-for-float.cpp

2021-12-07

• Symbolic Constants

• Exercise: Fahrenheit Table Using Macros

  Solutions:

  • fahrenheit-nonconst.cpp (a stupid bug)

  • fahrenheit-const.cpp (using C preprocessor macros to prevent stupid bug)

• Character I/O

• Exercise: wc For The Poor

• Arrays

• Exercise: Character Histogram

  

  • Solution: histogram.cpp

2021-12-08

• Reiterating on Exercise: Character Histogram

  • while ((c = getchar()) != EOF) { ... }: assignment has a value (DRY: don’t repeat yourself)

  • Arrays (and everything else) in C are not range checked ⟶ input needs verification

  • How far can I write past the end of an array? ⟶ out-of-bounds-write.cpp

    • From the histogram example: what happens if we receive an iso-8859-1 Umlaut character, say “ö”. That character is sure not within range [0,128).

      

    • From the smaller-scale canary example.

      

  • Aside: C has no bool datatype (C++ has) ⟶ infinite-loop.cpp

• Functions

• Exercise: Forward Declaration

  Solution: power.c

• Character Arrays

  Char array (i.e., string) walkthrough: strings-wtf.cpp

  Massacre using strcpy …

  

• Exercise: Read Line Into String from stdin

• Lifetime of Variables

  Global variables: global-vs-local.cpp

• Type System

• Variable Names

• Data Types, Sizes

• Type Conversions

  Demo code: type-system.cpp

  Massacre resulting from mixing signed and unsigned integers …

  

• Pointers and Arrays

  • Pointers and Addresses

    • pointer-basics.cpp

    • pointer-brainfuck.cpp

  • Exercise: Function That Swaps Two Variables

    • Fix that to actually swap the caller’s variables: swap-nok.cpp

2021-12-09

• Morning wakeup, talking about what happened, questions

  • Reiterate on canary and memory errors in general. Security holes, blah, blah. C is the root of all evil.

    

  • argv; that double pointer thing.

    Compose an array like argv manually (argv-manually.cpp)

    

  • Double pointers, generally

    double-pointer.cpp

    

  • Pointer arithmetic, killing canaries sitting in a row next to an integer

    

  • The same can happen to a function’s return address

    

  • Useful use of pointers: singly linked list

    

• Resolve Exercise: Function That Swaps Two Variables

  • swap-nok.cpp

  • Not working

    

  • Working

    

• Continuing with Pointers and Arrays

  • Pointers and Arrays

  • Commandline Arguments

    Hack a little argv example

• Structures

  • struct: Basics

  • struct: Functions

  • typedef: Type Alias

• Functions and Program Structure

• Pointer Recap: pointer-recap.cpp

2022-01-24

Undefined Behavior

Undefined behavior ist commonplace in C. C++ takes long turns to get undefined behavior out of the way. For example:

• Array bounds read/write

  • It is perfectly ok to read and write past the boundaries of an array. At least this is ok for the compiler; occasionally the program will exhibit undefined behavior - for example when you write into variables in the neighborhood. See undefined-behavior.c.

  • C++ brings data structures like std::vector that can do this better. See undefined-behavior-c++.cpp.

• Integer overflow bugs are the norm - happily mix signedness and unsignedness, happily mix various integer widths. See overflow-recap.cpp.

• Structures (struct) recap; struct-recap.cpp, again with an array bounds write.

• Pointers recap; pointer-recap-recap.cpp.

• Functions recap; power-recap.c.

Modularization

• What’s that separate compilation unit thing? How do we use the C preprocessor? Dogmatically introducing include guards!

  • Basics

  • Extern/Global Variables

  • Header Files

  See an example (in C, largely) here.

2022-01-25

C++ and OO (Classes)

• Introduction

• Classes and Objects

• Default Constructor

• Custom Constructor

  • Exercise: Transform struct User Into A Class

Modularization (again)

• Static Variables

  Livehacking this:

  • One file

  • Another file

2022-01-26

Modularization: Repeating Important Topics (Quickly)

• Extern/Global Variables

• Header Files

• C Preprocessor: Basics

• C Preprocessor: More

  Livehacking: Solving the problem (duplicate includes) step by step: include guards

Classes (continued)

• More Constructors, Destructors

• Object Copy (And Resource Management): There Be Dragons

  • Livehacking: Writing a string class by hand: resource management and copy

• Overloading

  Livehacking:

  • Overloading the max() function

  • Using std::string’s overloaded comparison operators

  • Explaining “immediate if”

• Methods

  • Exercise: Simple Method (Users Age By n Years)

2022-01-27

• Good-morning-exercise: Exercise: Access Methods for Members

  (See Classes and Objects for private and access methods)

  Solution see here

• Methods

  Livehacking

  • const in ol’ C: const-c.cpp

  • const in C++: const-cpp.cpp

  Exercise

  • Exercise: Use const

• this

• References

  Livehacking: excursion, back to parameter passing

  • swap(), revisited using references instead of pointers: parameter-passing.cpp

  • Using const with struct types: parameter-passing-struct.cpp

  

• Temporaries, by example. See live-hacking/mystring/temporary.cpp.

2022-01-28

• Exercise: Default Constructor (was: Arrays of Objects)

Standard Template Library: Container Templates

• Standard Template Library: Basics

  Livehacking: pointer arithmetic, using a C array of struct User: user-pointerarith.cpp

• Exercise: Use std::vector in UserDB

• sort<>

• binary_search<>: On Sorted Sequence

• lower_bound<>: On Sorted Sequence

• Sequential Containers

2022-01-31

• Exercise: Insert a User into UserDB

• Exercise: Search a User By Lastname

2022-02-01

Algorithms

• std::copy; copy.cpp

  

• std::find; find.cpp

• std::find_if; find_if.cpp

• std::sort; sort.cpp

• std::binary_search; binary_search.cpp

  

Functors

• Using std::for_each; for_each-functor.cpp

• Using std::find_if; find_if-functor.cpp

Operator Overloading

• Operator Overloading

• Live-hacking: operator-overloading.cpp

Unified Modeling Language (UML)

Wikipedia

• UML class diagrams

  

• UML sequence diagrams

  

Exercise (Using All From Today)

• Exercise: Search a User By Lastname (std::find_if)

  For those who chose to return a pointer from UserDB::search_by_lastname() … this is how to convert a const_iterator to a pointer:

  

2022-02-02

• Resolve exercise from yesterday

Associative Container: std::map

• Functors: overloading operator()()

  • Binary function: bool operator(l, r), as required for example by std::sort

    • Problem: calloperator-problem.cpp

    • Solution: calloperator-solution.cpp

  • std::sort<>(), the problem: using a binary function: sort-problem.cpp

  • Solution: write a functor class (still not pretty, too much coding): sort-solution.cpp

  • Introducing Lambda: sort-lambda.cpp

• Associative Containers

  Not much in there though ⟶ live hacking

Exceptions, and Exception Handling

• Basics

• try - catch

• Exercise: Search, “User Not Found” Exception

• Livehacking

  • Original problem: clumsy (but comprehensive) C-style error handling (using a return value to transport the error, and an “output parameter” for the actual result). exceptions.cpp

  • Only slightly better: using std::pair<> to transport both error and result as return value. exception-pair.cpp

  • Throwing std::exception (and not catching it). exception-exc.cpp

  • Catching std::exception. exception-handling.cpp

  • Replacing std::exception with a custom exception. exceptions-custom.cpp

2022-02-03

• operator<<(std::ostream&): how to, using (again) class Point: live-hacking/ostream-operator.cpp

• Exercise: Paint the American Flag Onto Standard Output

  One possible solution, american-flag.cpp. Slightly over-engineered, to show how you write your own operator<<().

• Exercise: Reverse a String

  Solution alternatives:

  • Manual, index-based iteration, naively using string::operator+=(): reverse-string-naive.cpp

  • In-place modification using std::reverse<>(): reverse-string-reverse.cpp

  • std::reverse_copy<>(): reverse-string-reverse-copy.cpp

• Exercise: Sum of Integers Coming From cin

  Solution (a history of iteration in C++, to the point where we do not iterate but use std::accumulate<>() instead): sum-ints.cpp

• Exit status again: live-hacking/exit-status.cpp

• Explaining libraries, and how they are created with CMake: exercises/joerg/userdb/CMakeLists.txt

2022-02-04

C++11: A New Language

• C++ >= 11

Dynamic Allocation, Smart Pointers

• Dynamic memory allocation

• Smart Pointers: std::unique_ptr, std::shared_ptr (And std::weak_ptr)

Multithreading

• Multithreading, C++ Memory Model

• Synchronization

Live hacked:

• Basics: thread-basics.cpp

• Start parameters: thread-with-start-parameters.cpp

• Lost increment (aka “Mother of All Race Conditions”): thread-lost-increment.cpp

• Using a mutex (“toilet door lock”): thread-no-lost-increment-mutex.cpp

• Same, but encapsulating the racy integer together with a mutex in a class that behaves like an integer: thread-no-lost-increment-mutex-beautiful.cpp

• For integers, though, there is a better way to safety - atomics: thread-no-lost-increment-atomic-fast.cpp

2022-02-07: Start of Exercise Week

• Moving to Linux: WSL2

• Install prerequisites

  $ sudo apt install cmake build-essential libsqlite3-dev libboost-all-dev libgtk-3-dev
  

• Unit testing framework documentation: Boost Test Library: The Unit Test Framework

• class UserDB is now an interface

  

• Into the wild …

  • Requirements not defined in prosaic words anymore: test driven development

  • Roman going mad: using wxWidgets to build a GUI on top of our user database

  • …