Compilers

A 2-post collection

on Programming, Rust, Macros, Compilers, The Basics, Low-level • 28 min read

Stack Machines and Where To Find Them

Ever tried googling "recursion"?

screenshot of a Google search for "recursion". The results begin with "Did you mean: recursion"

There's something quite peculiar about recursion. Every developer and their dog has heard of it at some point, and most developers seem to have quite a strong opinion about it.

Sometimes, they were taught about it in college. Some old professor with a gray beard and funny words (the hell's a cons cell? why are you asking if I want to have s-expr with you?) made them write Lisp or Caml for a semester, growling at the slightest sign of loops or mutability to the poor student whose only experience with programming yet was Java-like OOP. Months spent writing factorials, linked lists, Fibonacci sequences, depth-first searches, and other algorithms with no real-world use whatsoever.

Other times, it was by misfortune. While writing code in any of their usual C-family enterprise-grade languages, they accidentally made a function call itself, and got greeted by a cryptic error message about something flowing over a stack. They looked it up on Google (or Yahoo? AltaVista? comp.lang.java?) and quickly learned that they had just stumbled upon some sort of arcane magic that, in addition to being a simply inefficient way of doing things was way too complicated for any

on Programming, Rust, Macros, Compilers, Code analysis • 17 min read

How I Learned to Stop Worrying and Love Macros

Rust macros are powerful, that's a fact. I mean, they allow running any code at compile-time, of course they're powerful.

C macros, which are at the end of the day nothing more than glorified text substitution rules, allow you to implement new, innovative, modern language constructs, such as:

#define ever (;;)
for ever { 
	...
}
https://stackoverflow.com/a/652802/2196124

or even:

#include <iostream>
#define System S s;s
#define public
#define static
#define void int
#define main(x) main()
struct F{void println(char* s){std::cout << s << std::endl;}};
struct S{F out;};

public static void main(String[] args) {
	System.out.println("Hello World!");
}
https://stackoverflow.com/a/653028/2196124

But these are just silly examples written for fun. Nobody would ever commit such macro abuse in real-world, production code. Nobody...

/*	mac.h	4.3	87/10/26	*/

/*
 *	UNIX shell
 *
 *	S. R. Bourne
 *	Bell Telephone Laboratories
 *
 */
 
...

#define IF		if(
#define THEN	){
#define ELSE	} else {
#define ELIF	} else if (
#define FI		;}

#define BEGIN	{
#define END		}
#define SWITCH	switch(
#define IN		){
#define ENDSW	}
#define FOR		for(
#define WHILE	while(
#define DO		){
#define OD		;}
#define REP		do{
#define PER		}while(
#undef DONE
#define DONE	);
#define LOOP	for(