Bootstrapping (compilers)
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Bootstrapping is a term used in computer science to describe the techniques involved in writing a compiler (or assembler) in the target programming language which it is intended to compile.
One may then wonder how the chicken and egg problem of creating the compiler was solved: if one needs a compiler for language X to obtain a compiler for language X, how did the first compiler get written? Possible methods include:
- implementing an interpreter or compiler for language X in language Y.
- another interpreter or compiler for X has already been written in another language Y; this is how Scheme is often bootstrapped.
- earlier versions of the compiler were written in a subset of X for which there existed some other compiler; this is how some supersets of Java are bootstrapped.
- the compiler for X is cross compiled from another architecture where there exists a compiler for X; this is how compilers for C are usually ported to other platforms
- writing the compiler in X; then hand-compiling it from source (most likely in a non-optimized way) and running that on the code to get an optimized compiler
Methods for distributing compilers in source code include providing a portable bytecode version of the compiler, so as to bootstrap the process of compiling the compiler with itself.
The first language to provide such a bootstrap was NELIAC. The first commercial language to do so was PL/I. Today, a large proportion of programming languages are bootstrapped, including C, Haskell, Scheme, OCaml, Pascal, Modula-2, Oberon, Factor and more.
