Bootstrapping (compilers)

In computer science, bootstrapping is the technique for producing a self-compiling compiler – that is, a compiler (or assembler) written in the source programming language that it intends to compile. An initial core version of the compiler (the bootstrap compiler) is generated in a different language (which could be assembly language); successive expanded versions of the compiler are developed using this minimal subset of the language. The problem of compiling a self-compiling compiler has been called the chicken-or-egg problem in compiler design, and bootstrapping is a solution to this problem. Bootstrapping is a fairly common practice when creating a programming language. Many compilers for many programming languages are bootstrapped, including compilers for BASIC, ALGOL, C, C#, D, Pascal, PL/I, Haskell, Modula-2, Oberon, OCaml, Common Lisp, Scheme, Go, Java, Elixir, Rust, Python, Scala, Nim, Eiffel, TypeScript, Vala, Zig and more. A typical bootstrap process works in three or four stages: Stage 0: preparing an environment for the bootstrap compiler to work with. This is where the source language and output language of the bootstrap compiler are chosen. In the case of a "bare machine" (one where no compiler for any language exist) the source and output are written as binary machine code, or may be created by cross compiling on some other machine than the target. Otherwise, the bootstrap compiler is to be written in one of the programming languages which does exist on the target machine, and that compiler will generate something which can execute on the target, including a high-level programming language, an assembly language, an , or even machine code. Stage 1: the bootstrap compiler is produced. This compiler is enough to translate its own source into a program which can be executed on the target machine. At this point, all further development is done using the language defined by the bootstrap compiler, and stage 2 begins. Stage 2: a full compiler is produced by the bootstrap compiler. This is typically done in stages as needed, e.