System programming notes

by Christopher J. Brody AKA @brodybits (Chris Brody)

LICENSE: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/legalcode, https://creativecommons.org/licenses/by/4.0/)

What

Lower-level programming of software components that are used by other systems programmers, higher-level applications programmers, and other experienced software systems engineers.

General reference with other characteristics: https://en.wikipedia.org/wiki/System_programming

Major characteristics:

• designed for certain types of hardware
• limited run-time library requirements
• direct memory access
• needs careful resource management
• not always easy to debug

Gotchas

Important gotchas include:

• Undefined behavior (see references below)
• Compound computational complexity (https://dev.to/supermanitu/what-does-big-o-notation-mean-anyway--1hea)
• compound software system complexity

Comparison

General types of software, with limited overlap:

• Application software (designed for specific tasks, SHOULD deal with UX)
• System software
• Enterprise software

General ref: https://en.wikipedia.org/wiki/Programmer

Additional (various levels of overlap):

• Embedded programming is generally a subset of systems programming.
• Game programming (possible overlap with system programming)
• Scalable software (overlap with other areas)
• Financial software (using languages such as C++ to achieve competitive efficiency)
• machine learning, neural networks, and other forms of AI

Kinds of system software

Some kinds of system software:

• kernel
• system libraries
• system services
• I/O and concurrency libraries
• other commonly-used libraries such as string manipulation, collections, etc.
• parallel software libraries and frameworks
• compilers
• VM
• interpreters
• other low-level application libraries

System programming languages

General-purpose:

• C
• C++
• Rust
• Java
• Objective-C and Swift
• Go
• AssemblyScript (https://github.com/AssemblyScript)

Middle:

• Haskel
• Erlang

Limited:

• Python
• JavaScript

Embedded scripting

• http://jsish.org/ - small but powerful JavaScript interpreter (seems to use ref. counting)
• Duktape
• JerryScript
• others from https://github.com/dbohdan/embedded-scripting-languages
• ROOT CINT C/C++ interpreter
• Cling C++ interpreter

Application stacks

Some application stacks using system programming:

• Jakarta EE née Java 2 EE
• Vert.x
• Node.js
• Cordova
• Jasonette to build native Android and iOS apps using JSON

Bridging

• N-API (Node.js, etc.)
• Nan (C++ wrapper for Node.js addons)
• libffi
• Cordova

Virtualization

General:

• VMs
• LLVM
• Web assembly (revolutionary)
• Eclipse J9

Projects:

• https://github.com/jakogut/tinyvm
• https://github.com/rabbitvm/rabbit
• https://github.com/zerovm/zerovm

Transpilers

• Emscripten

Middleware

• OpenMQ, Zero MQ, etc.

Awesome lists

• https://github.com/aleksandar-todorovic/awesome-c
• https://github.com/fffaraz/awesome-cpp
• https://github.com/rigtorp/awesome-modern-cpp
• https://github.com/uhub/awesome-cpp

Tools

• http://klee.github.io/ - LLVM-based tool that creates test cases from all possible paths through code

Important tips

Undefined behavior

Undefined behavior in C and C++:

• https://hackernoon.com/so-you-think-you-know-c-8d4e2cd6f6a6
• https://kukuruku.co/post/i-do-not-know-c/
• http://blog.llvm.org/2011/05/what-every-c-programmer-should-know.html
• https://blog.regehr.org/archives/213

storing pointers as integers

Best to use intptr_t and uintptr_t, now standardized for C and C++.

ptrdiff_t (alt): as taught in a Safer C (http://www.saferc.com/) course (Eindhoven, NL in September 2011):

In C and C++ ptrdiff_t is was the safest way to convert between pointers and integer values. NULL is usually but NOT required to be (void *)(0). To convert pointer to ptrdiff_t:

ptrdiff_t mydiff = (unsigned char *)myptr - (unsigned char *)NULL;

To convert stored ptrdiff_t value to pointer:

mytype_t * myptr = (mytype_t *)((unsigned char *)NULL + mydiff);

Recommended reading: https://www.viva64.com/en/a/0050/

Counterpoint: https://blogs.msdn.microsoft.com/david_leblanc/2008/09/02/ptrdiff_t-is-evil/

Other resources:

• https://www.codeguru.com/cpp/cpp/cpp_mfc/general/article.php/c16465/About-sizet-and-ptrdifft.htm
• https://software.intel.com/en-us/forums/intel-c-compiler/topic/534769
• http://cpgotchas.blogspot.com/2008/02/sizet-ptrdifft-and-offt.html

WebAssembly

WebAssembly vs LLVM IR format:

• WebAssembly/design#188 - discussion of why WebAssembly does not share the same binary format with LLVM

Additional: WebAssembly may be designed to better capture loops than LLVM IR.

Storage

Non-replicated:

• SQLite

Replicated:

• Redis

Other

Financial software sometimes uses low-level languages such as C++ to be competitive in terms of computational efficiency, low latency, etc.

Recommended resources

Some recommended resources:

• http://www.stroustrup.com/Programming/25_embedded.ppt
• other http://www.stroustrup.com/Programming/lecture-slides.html
• other results of https://www.google.com/search?q=stroustrup+systems+programming
• http://www.stroustrup.com/abstraction-and-machine.pdf
• http://www.modernescpp.com/index.php/requirements-of-embedded-programming
• http://www.modernescpp.com/index.php/component/jaggyblog/objectoriented-generic-and-functional-programming
• http://www.saferc.com/ (book and training)
• http://www.databorough.com/Five-Reasons-to-Measure-the-Complexity-of-Your-Software.html