__traits(documentation, X)

[H. S. Teoh]

On Wed, Jan 17, 2018 at 06:24:50PM +0000, Simen Kjærås via Digitalmars-d wrote:
[...]
> enum a = import(__FILE__);
> static if (a.indexOf("//") > -1) {
>     fireZeMissiles();
> }
[...]

OTOH, this combination of string import and self-referencing __FILE__
opens up a host of curious possibilities (all of which already work
today, btw):

1) Trivial self-reproducing program in D:

	import std.stdio;
	void main() { write(import(__FILE__)); }

2) Self-checking programs:

	import std.algorithm;
	static assert(import(__FILE__).canFind("\n/**"),
		"Dude, why did you remove the ddoc comment?!");

	/** Remove this comment to get a compile error */
	void main() {
	}

3) Underhanded / deceptive "self-modifying" code:

	version(none) {
		// This code will never get compiled, right? Right???
		import std.stdio;
		void main() {
			writeln("Launch nuclear missiles");
		}
	} else {
		mixin(() {
			import std.array : replace;
			return import(__FILE__).replace("none", "all");
		}());
	}

These are just trivial examples, of course.  One can easily imagine more
sophisticated variations that can do all sorts of weird / dangerous
things.

Imagine an advanced version of (2), for example, code that will force a
compilation error if it wasn't formatted correctly.

Or an advanced form of (3) where the real program code is inside an
encrypted comment written in a different language that gets compiled
into D by a CTFE compiler.

Or a CTFE implementation of AST macros that uses libdparse to parse
itself, apply modifications, and mixin. :-D


T

-- 
"Maybe" is a strange word.  When mom or dad says it it means "yes", but when my big brothers say it it means "no"! -- PJ jr.