[EMAIL PROTECTED] wrote:
* multiple results can be returned via C++ pair<a,b> template, if this is
efficiently implemented in gcc
There's a -freg-struct-return option in 2.x, 3.x and 4.x. I think it's off
by default on many architectures.
* recursive definitions translated into the for/while loops if possible
I think recent versions of GCC do a good job of this. See
http://home.in.tum.de/~baueran/thesis/
All of this efficiency stuff aside, there's a big problem you're neglecting:
GARBAGE COLLECTION. For a language that allocates as much as Haskell I think
a conservative collector is absolutely out of the question, because they
can't compact the heap and so allocation becomes very expensive. A copying
collector has to be able to walk the stack and find all the roots, and that
interacts very badly with optimization. All the languages I've seen that
compile via C either aren't garbage collected or use a conservative or
reference-count collector.
The closest thing I've seen to a solution is the technique used in Urban
Boquist's thesis, which is to put a static table in the executable with
information about register and stack usage indexed by procedure return
point, and use that to unwind the stack and find roots. Some C compilers
(including gcc) support debugging of optimized code, so it might be possible
to parse the debugging tables and extract this information. As far as I
know, no one has ever looked into the feasibility of doing this, which is
kind of surprising since root-finding is probably the single biggest
obstacle to compiling functional languages via C.
-- Ben
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