I knew I'm not crazy :-) I knew there would be at least somebody, who will see what I meant :-)
On Wed, Nov 9, 2011 at 12:17 PM, foobar <f...@bar.com> wrote: > Don Wrote: > >> On 07.11.2011 14:13, Gor Gyolchanyan wrote: >> > After reading >> > >> > http://prowiki.org/wiki4d/wiki.cgi?DMDSourceGuide >> > https://github.com/gor-f-gyolchanyan/dmd/blob/master/src/interpret.c >> > >> > I had a thought: >> > Why not compile and run CTFE code in a separate executable, write it's >> > output into a file, read that file and include it's contents into the >> > object file being compiled? >> > This would cover 100% of D in CTFE, including external function calls >> > and classes; >> > String mixins would simply repeat the process of compiling and running >> > an extra temporary executable. >> > >> > This would open up immense opportunities for such things as >> > library-based build systems and tons of unprecedented stuff, that I >> > can't imagine ATM. >> >> First comment: classes and exceptions now work in dmd git. The remaining >> limitations on CTFE are intentional. >> >> With what you propose: >> Cross compilation is a _big_ problem. It is not always true that the >> source CPU is the same as the target CPU. The most trivial example, >> which applies already for DMD 64bit, is size_t.sizeof. Conditional >> compilation can magnify these differences. Different CPUs don't just >> need different backend code generation; they may be quite different in >> the semantic pass. I'm not sure that this is solvable. >> >> version(ARM) >> { >> immutable X = armSpecificCode(); // you want to run this on an X86??? >> } >> > > I think we discussed those issues before. > 1. size_t.sizeof: > auto a = mixin("size_t.sizeof"); // HOST CPU > auto a = size_t.sizeof; // TARGET CPU > > 2. version (ARM) example - this needs clarification of the semantics. Two > possible options are: > a. immutable X = ... will be performed on TARGET as is the case today. > require 'mixin' to call it on HOST. This should be backwards compatible since > we keep the current CTFE and add support for multi-level compilation. > b. immutable x = ... is run via the new system which requires the function > "armSpecificCode" to be compiled ahead of time and provided to the compiler > in an object form. No Platform incompatibility is possible. > > I don't see any problems with cross-compilation. It is a perfectly sound > design (Universal Turing machine) and it was successfully implemented several > times before: Lisp, scheme, Nemerle, etc.. It just requires to be a bit > careful with the semantic definitions. >
