Programmieren mit C (2021-06-14 - 2021-06-18)

Training Information

Start

Montag 14.6.2021, 9:00

Offizielle Beschreibung

tecTrain

Material

• Slides, C

• Slides, CMake

• Slides, GNU Make

• Github Repository

CPA Exam

• Sample Questions

Preparation: Tools

• C/C++ for Visual Studio Code

• Get started with CMake Tools on Linux

• CMake download

Log

Day 1

• Introduction (from the C slides)

  • Hello World

  • Variables and Arithmetic

  • for Loops

  • Symbolic Constants

  • Character I/O

• Occasional live hacking

  • hello.c

  • fahr.c

  • fahr-for.c

  • wc.c. This is going to be morphed into a formal state machine tomorrow.

Day 2

State machine

It turns out that the correct solution to exercise on slide 37 of the slide deck is a state machine. It enables us to correctly cover all corner cases (e.g. multiple consecutive spaces between two words) …

• wc.c became a state machine, implementing the above state chart. Using if-then-else to cover the states.

• Introduced the switch statement (slightly :-) deviating from the regular course flow); changed the state maching to use that instead of if-then-else. See wc-switch.c

Regular Course Topics

• Introduced pre and post increment operators (again severely deviating). See pre-post-increment.c.

• Ah, arrays: leading to the “histogram” exercise (slide 41 from the slides). Solution see here on Github

• Functions. Slides 44ff. from the slides (the power() function from the K&R book) as a live hacking gig. See here on Github.

• Quick CMake intro, as a preparation for the upcoming group project. Confusing people.

Day 3

Development Tools (Git & CMake) Installation Massacre

• Git. See here for instructions about how to use Git with VS Code. It turns out that

  • Git Extension Pack guides users through workflows pretty well. Staging, commits, merges.

  • Except that we appear to have problems with Github authentication, which is why we use Github Desktop for remote stuff like clone, push, pull.

• CMake. Doze installation; use the MSI (the installer package).

Regular Course Material

• Fast run-through: slides 64-75

• Stop at enums/76: morph wc.c state machine into a perfect enum candidate. This is the time to …

  • Show how to use enum in the state machine from above.

  • Enable -Wswitch-enum (nowadays included in -Wall, apparently) CMakeLists.txt

  • Show how default:-less switch statements, enum``s, and ``-Wswitch-enum can work together and help me maintain code better.

  Program see here.

• “Variable Definitions” section. Slides 77ff. Emphasize on local variables (this is what we saw so far) more. Lifetime, initialization, etc.

• Almost skip 81-88. Operators, boring.

• Hard stop at “Type Conversions”, slides 89ff. Make people run away screaming (intentionally).

Group Project Kick-Off :-)

Kick off “group project”. Git, CMake, and team development, with rather artificial use cases. But anyway, these are use cases. See here.

Exercise: in the group-project/ directory,

• Build a program that uses declarations from db.h, to

  • Iterate over what is in the user database ⟶ userdb alongside num_users, external variables.

  • Write CSV output.

• Add build instructions to group-project/CMakeLists.txt.

• When done, commit and push to Github.

Day 4

Regular Course Material

• Repeat external, local vs. global variables, visibility

• Pointers: 199ff from the slides. Address space and pointers:

  

  Entire address space

• Pointers: slide 203, “More Examples”: pointers.c

  

• Slide 204ff, “Pointers as Function Parameters”: pointers-as-function-parameters.c

• Slide 208ff, “Pointers and Arrays”: pointer-arrays-arithmetic.c

• Slide 220ff, “Commandline”: pointers-argv.c

• C++: STL, Iterators, and their relation to pointer arithmetic. pointer-array-in-c++.cpp.

• struct chapter, slides 222ff

  • Live-hack the struct point story from the slides. Show how an API could look like. point.c.

Exercise: Encapsulate Index Access to userdb

• In your CSV export programs, replace the direct index access to userdb with the API function db_get_user_at_index() from db.h.

• userdb must not be seen anymore in any user code.

Group Project (Use Case Driven Course Flow :-) )

• Hide implementation details: use static for the userdb array. (More on slides 298ff.)

• Add user record to DB. Have to use strcpy(). Here a sketch of the internal “organisation”.

  

Day 5

Pointer Recap

• strlen(). Man page

  

• strcpy(). Man page.

  Here is how to produce undefined bahavior by allocating too less space for the target string.

  strcpy-undefined-behavior.c

  #include <string.h>
  #include <stdio.h>
  
  int main(void)
  {
      char src[] = "abc";
      char dest[2]; // far too less, should be at least 4!
  
      strcpy(dest, src);
      printf("src: %s, dest: %s\n", src, dest);
  
      return 0;
  }
  

  

• Pointer massacre: strtol(). Man page.

  Live hacking example: str-to-int-conversion.c

  

On With Group Project

• Show how error codes can be implemented

  • Error code definition using an enum. db.h, enum Error.

  • Error code stringification, db_error_string().

    • db.h, declaration.

    • db.c, definition. Note how we are using a default-less switch statement, together with -Wall (implicitly enabling -Wswitch-enum) in the toplevel CMakeLists.txt.

• Valgrind. Here’s a YouTube Video on it.

• File IO: binary vs. text. Here’s a YouTube Video on it.

• CMake: show how you build and use libraries. group-project/CMakeLists.txt.

Further Information

Here’s some literature :-) to study as a preparation for our upcoming C++ course. Unfortunately, there are no absolute high-quality tutorial videos out there - one reason might be that those languages are not as sexy anymore as, for example, Python (where you can pick your favorites from a large pool of high quality material).

C++ Basics

• C++ Strings - Intro and Comparison to C Strings. Caleb Curry.

• C++ Examples - Pass by Value vs Reference vs Pointer. Caleb Curry.

Pointers, Pointer Arithmetic, and the Standard Template Library (STL)

• C++ Pointers - Finally Understand Pointers. Caleb Curry.

• Pointer Arithmetic. Pointer Arithmetic in C; good to understand before going into C++ containers and iterators.

• STL Containers - Learn Modern C++. A somewhat boring but comprehensive overview of available C++/STL datastructures and their runtime behaviour.

• STL Vector.

• STL Map.

• STL Set.