Re: Why Can't We Build a C Compiler?

>"C is not a `very high level' language, nor a `big' one ...". Its syntax
>and semantics are well-defined.


I don't think this is the case, although I'm probably out of touch
with C standards. I thought there were problems with aliasing and so
on which weren't properly resolved. And I won't even mention the
hornet's nest that's opened when you start to think of all the
interactions with the macro preprocessor.


John's comment:
>[This point is well taken. I would think that with all of the theory
>available to compiler writers, compilers would be prime targets for software
>engineering techniques such as formal verification, of parts at least. Beats
>me why not. -John]


This is the approach we've taken with the ML project. Standard ML is,
to my knowledge, the only language to have a complete formal semantics
(which is *not* huge - 97 pages). Does Ada have one? How big is it?
The semantics serves as a reference for building compilers - there
are, I believe, 3 compilers respecting the semantics. I'm not going
to claim that they're all bug-free or absolutely conformant yet - ML
is a language very different from conventional languages like C or
PASCAL, and the implementation techniques are still very new - but the
task of compiler development is possible with small teams of compiler
writers (by small, I mean 1 or 2 persons).


Nick.
--
Nick Rothwell, Laboratory for Foundations of Computer Science, Edinburgh.
nick@lfcs.ed.ac.uk <Atlantic Ocean>!mcvax!ukc!lfcs!nick
--

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