That's interesting, writing a DSL that compiles to C. I've actually inerviewed Gerard Holzamann twice, the first time when he received the ACM Software System Award in 2002 [1] and in 2008 after he moved to JPL [2]. What they use to test distributed software is the Process Meta Language (Promela) which models communication between distributed processes. Now Spin checks all possible models for deadlock, liveness etc. You can also use asserts to test conditions, just as in C. It also uses LTL (linear temporal logic) to formulate statements like, "will the railroad crossing always eventually open" and such. Two articles about Spin are [3] and [4]. Unfortunately, all four are in Dutch, but, hey, surely somebody here must be able to read that language <g>. The articles on Spin contain listings in Promela. Now, what Gerard Holzmann told me in the interview, is that NASA is very conservative in it's use of software tools. They don't use C++, just C, and a well defined version of the GNU C compiler at that. The coding standards, which even prohibit the use of C pointers, are aimed to keep everything as simple as possible. Just imagine hundreds of people working over many years to produce code where any error, how trivial it may be, will occur millions of miles away, cost hundreds of millions of dollars, and could damage the reputation of the company and its future funding. Now, if you can use a DSL to make embedded software absolutely failsafe, that would certainly grab NASA's attention. But again, they are very conservative, it seems... [1] http://muitovar.com/pub/pdf/holzmann.pdf [2] http://muitovar.com/pub/pdf/acmaw.pdf [3] http://muitovar.com/pub/pdf/spin1.pdf [4] http://muitovar.com/pub/pdf/spin2.pdf On Tue, 2010-06-08 at 18:27 +0200, Heinrich Apfelmus wrote:
Michael Schuerig wrote:
I was dumbfounded, although I have known all this. I have no personal experience with either embedded or real time software, but I've been aware that C still is the most popular language for that purpose and that coding standards are very restrictive.
The real reason behind my surprise was, that I was wondering how more modern languages could make inroads into such an environment. Haskell without recursion and dynamic memory allocation? Hard to imagine.
I have absolutely no experience with real time system, but if I were tasked to write with these coding standards, I would refuse and instead create a small DSL in Haskell that compiles to the requested subset of C.
After all, the question is this: why use C if you don't actually use C? The reason is probably that designing/writing a proper DSL is considered too error prone, but with today's theorem provers, this should no longer be the case.
Regards, Heinrich Apfelmus