[Question]
  [
We've had lots of questions about [quine](/questions/tagged/quine "show questions tagged 'quine'")s, programs where the source code and output are identical. For compiled languages, there are other combinations: we've already had [a question](https://codegolf.stackexchange.com/q/8956) about writing a program where the executable and output are identical. But there's one combination left.
## The task
Using a compiled language (i.e. a language which has a compiler that converts source code to executables, which are then executed), write a program which, when compiled, will produce an executable which is bit-for-bit identical to the source code.
## Clarifications
* As with all [quine](/questions/tagged/quine "show questions tagged 'quine'") challenges that do not state otherwise, you must obey the site's [proper quine rules](https://codegolf.meta.stackexchange.com/search?q=proper+quine). In particular, this excludes zero-byte programs, and programs where all the commands compile into themselves.
* At least for this challenge, it doesn't matter what the resulting executable does when run; this is purely a [compile-time](/questions/tagged/compile-time "show questions tagged 'compile-time'") challenge. (If it turns out to be easy, I'm sure that someone will end up posting a "write a program where the source code, executable and output when executed are all the same" challenge, but you don't need to go to that level of complexity for *this* challenge.)
* Your program will, in effect, be a [polyglot](/questions/tagged/polyglot "show questions tagged 'polyglot'") between the source language, and the language it compiles into. This means that you will need to pick a source language, and executable format, for which such a combination is possible.
* Multistep compiling (e.g. compiling an esoteric language into C, which then compiles into an executable) is a legal way to answer the problem. However, this is limited to the use of three compilation steps at most (in order to avoid answers that encode the desired output in the sequence of compilers used rather than in the source code).
* Don't use unusual compiler flags to loophole the question via abusing the `-D` option of a C compiler to hide code (or similar techniques that move code from the program into the compiler flags). You might well need to use unusual compiler flags to produce the executable in the right format, but these should be flags that would generally be useful for compiling programs, not flags specific to the program you've written (and that embed information about it); remember that on this site, the language you're using is defined by the interpreter and compiler flags that you're using.
* Likewise, it's possible that your solution will require a specific filename for the source code; in order to prevent you using this to store code, any specific filename should consist of one character, possibly followed by a standard file extension for the language you are using.
* Please state the exact compiler and version you're using to compile your program, together with the compiler flags you need to build it, because your answer may be hard to reproduce / verify for correctness otherwise; solutions to this question are likely to inherently be somewhat compiler-specific.
* This problem is mostly aimed at compilation into executable formats used by operating systems, but if you have a language that compiles into something else (e.g. bytecode), feel free to submit an answer for that setup, too, even if it won't be quite as impressive. We aren't in the business of unnecessarily restricting what languages you can use here.
## Victory condition
This is effectively a [code-golf](/questions/tagged/code-golf "show questions tagged 'code-golf'") (minimize size of the source) and sizecoding (minimize size of the executable) challenge at the same time (because the two are the same): in this challenge, a program is considered to score better than another if it has a shorter length in bytes. So once you've figured out how to solve this problem at all, you can see if you can do better by fitting the program into fewer bytes.
  
[Answer]
# [CoffeeScript to JavaScript](https://coffeescript.org), 2 bytes
```
a;
```
[Try it](https://coffeescript.org/#try:a%3B)
* `a` is compiled into `a;`. You may [try it here](https://coffeescript.org/#try:a).
* `;` is compiled into nothing. You may [try it here](https://coffeescript.org/#try:%3B).
---
Without ban "programs where all the commands compile into themselves", [js2js](https://eleks.github.io/js2js/) would be a much better choice, IMO.
]