Microsoft 'compiler-as-a-service' project emerging from secrecy

'Roslyn' under development since 2011, and recent Microsoft blog post hints rewrite of Visual Basic and C# compilers could preview soon

For more than two years now Microsoft has been working in near-complete silence and secrecy, with only the occasional blip of publicity, on a new compiler technology.

Described in various places as a "compiler-as-a-service" system and code-named "Roslyn," the new technology purports to be nothing less than an inside-out rewrite of the way Microsoft's Visual Basic and C# compilers work.

Hints about Roslyn emerged back in 2011, when it was revealed that information generated about the program by the compiler can in turn be reused by the program itself. This allows the programmer much deeper access than before into how their own programs work when compiled and would even permit tasks like dynamic variable typing. (C# and Visual Basic are statically typed languages.)

The demonstration back then included such eye-opening possibilities as converting a Visual Basic program to C# (and back), but was still considered a highly experimental technology. Consequently, no time frame was given for when Roslyn's technology would be made part of Microsoft's Visual Studio product family.

Then a long silence descended upon the project, punctuated only by a Community Technology Preview (CTP) for the project in September 2012.

Just this week, new word about the project emerged by way of a blog post at, "Throwing the Big Switch on Roslyn," in which Matt Gertz, Visual Studios managed languages development manager, talks at length about what Roslyn is, where it stands, and what it's intended to do.

First and most significant was the way Roslyn was "dogfooded" -- used by the team developing it for day-to-day work. "We compiled & assessed over 60,000 projects, large and small, both internal and external to Microsoft (including flagship Microsoft products)," claims Gertz, and by the end of October switched the entire Visual Studio organization over to using Roslyn internally. "I'm happy to say that all that prep work set up us well -- since The Big Switch, we've run into no major issues!"

Second, and most tantalizing, is a note at the end of the post that hints at how regular previews will be starting up again soon, and "we can hardly wait to show you what we've been up to as we've been solidifying Roslyn!"

Mary Jo Foley of ZDNet picked up on the post, but was unable to wring further details out of her usual batch of deep Microsoft contacts.

The Register speculates, none too outlandishly, that full details are likely to drop around the time of Microsoft's next Build conference, which is set to happen April 2-4, 2014.

One possible implication of this hint dropping is that Roslyn's compiler-as-a-service approach may become a direct complement to the reinvention of Visual Studio as an online service. It's not yet clear how Roslyn would play into this, but one possibility is that the Roslyn code-inspection tools could be used to analyze and fine-tune cloud-hosted, parallel-programmed apps that make use of the latest C# language features for such things. Being able to use live internal feedback about the compilation of such programs ought to be a major boon for those building their software directly in the cloud -- and plenty of other places, too.

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