lecture-4-programming-constructs

Programming Constructs

This lecture is part of a 4-lecture series covering hardware/software interaction. In this specific lecture, we explore under the hood details of selected programming constructs, such as variables, functions, classes, try/catch etc. We try to imagine how they might be implemented at a hardware level, and validate our understanding with actuals. In the process, we develop a deeper understanding of these constructs in programming languages.

Pre-read

• Which language is faster? C? Java? Rust? Go? Is speed a "language" thing?
• ⁠Go through this article to understand memory layouts of running programs. You don't have to understand the C part, focus on just the high level picture & understanding.
• ⁠Stack vs Heap - is one faster than the other? If yes, which one?
• ⁠Other than infinite recursion, are there other ways to encounter a stack overflow? What's really happening behind the scene?
• ⁠For all the pre-reads, going through them as a group (of 2-4) is highly encouraged.

Files

• memlens.cpp - the main program we use to explore internals of programs. See Compilation step.
• memlens.hpp - header file for memlens.
• memlens-linux.hpp - header file for linux specific implementation pieces. Not required to be understood for this lecture.
• memlens-macos.hpp - header file for macos specific implementation pieces. Not required to be understood for this lecture.
• memlens-windows.hpp - header file for windows specific implementation pieces. Not required to be understood for this lecture.

Compilation

• On Linux/macOS: make memlens
• On Windows (in Visual Studio cmd prompt): cl /EHsc memlens.cpp

Assignments

• Is JVM a Harvard Architecture? Use lecture3 (slide 18) to refresh the JVM's memory model.
• Figure out how non-primitive data types are returned - via registers? via stack? If the latter, where is the allocation made (caller or callee stack)?
• Figure out the $default mechanism in Kotlin for handling default parameter values
• Given what you know about functions, discuss how lambdas (anonymous functions) get implemented.
• async/await is an increasingly popular programming construct which allows one to "schedule" blocks of logic (code). Knowing what you know about code, stack and heap, how would you think about the underlying implementation of such a construct.
• Research why address of code (also called text) section doesn't usually start from address 0. While researching, be thoughtful to critically assess the explanation, instead of just blindly accepting it.