ruby2c 1.0.0 beta 2 released

[Ryan Davis]

We've released ruby2c 1.0.0 beta 2!

RubyToC has the following modules:

Rewriter - massages the sexp into a more consistent form.
TypeChecker - type inferencer for the above sexps.
RubyToC - converts a ruby (subset) sexp to C.

and the following tools:

translate.rb - Translates a given file to C.

Understand what we mean by beta. It means we need eyes on it, it means
it was ready enough to put out in the wild, but it also means that it
isn't ready for any real use.

What can it do?

Well, currently it can pass all of its unit tests (325 tests with 512
assertions) and it can translate nice simple static algorithmic code
into C without much problem. For example:
& cat x.rb
class Something
def blah; return 2+2; end
def main; return blah; end
end
& ./translate.rb x.rb > x.c
& gcc -I /usr/local/lib/ruby/1.8/powerpc-darwin x.c
x.c: In function `main':
x.c:17: warning: return type of `main' is not `int'
& ./a.out
& echo $?
4

What can it not do?

More than it can.

It can't (and won't) translate dynamic code. Period. That is simply
not the intent.

It probably can't translate a lot of static code that we simply
haven't come across or anticipated yet. Our tests cover a fair amount,
our validation runs cover a lot more than that, but it is still fairly
idiomatic ruby and that puts us at being better at certain styles of
coding and much worse at others.

It is also simply rough around the edges. We've rounded out the rdoc
but haven't done a thing for general documentation yet. These are on
our list, and rather high on our priority list, but we just haven't had
the time yet. For now, check out the rdoc and the PDF presentation that
we've had up for a while.

PLEASE: file bugs! We need feedback and we'd like to be able to track
it. The ruby2c project is on rubyforge and I'm getting the trackers set
up today as well.

CHANGES:

*** 1.0.0-beta2 / 2004-02-15

+ 1 minor enhancement
+ Added post-condition while/until support and tests.
+ 4 bug fixes
+ Fixed bug:1422: Escape newlines to prevent multi-line strings in C.
+ Fixed bug:1429: Arrays of strings are not being properly.
+ Fixed bug:1447/1448: Readme file's website and added ParseTree
dependency.

 

[Luke Graham]

I just want to ask if

puts "foo" + 2

will fail before gcc-time? Or do you use rtti so typing is still put
off till run-time?

 

[Hal Fulton]

I just want to ask if

puts "foo" + 2

will fail before gcc-time? Or do you use rtti so typing is still put
off till run-time?

I'm not sure it *could* be smart enough to catch that.
There could be a Integer#to_str defined somewhere, perhaps
at runtime.


Hal

 

[Ryan Davis]

I just want to ask if

puts "foo" + 2

will fail before gcc-time? Or do you use rtti so typing is still put
off till run-time?

It _should_ fail, but currently doesn't. We don't do RTTI, we do type
inference at translation time, before the C emit phase, so this should
be caught. I'm filing a bug now.

 

[Ryan Davis]

I'm not sure it *could* be smart enough to catch that.

Sure it can!

There could be a Integer#to_str defined somewhere, perhaps
at runtime.

Remember, ruby2c is all about static conversion, not dynamic. I suggest
you read our propaganda at:

http://www.zenspider.com/~ryand/Ruby2C.pdf

 

[Garance A Drosehn]

Checking out the writeup on Ruby2C at:

http://www.zenspider.com/~ryand/Ruby2C.pdf

there is one thing about the example on page 25 (of the pdf)
which concerns me a little bit. The example has:

class MyTest
def factorial(n)
f =3D 1
n.downto(2) { |x| f *=3D x }
return f
end
end

turn into:

static VALUE factorial(VALUE self,
VALUE _n) {
long n =3D NUM2INT(_n);
long f;
long x;
f =3D 1;
x =3D n;
while (x >=3D 2) {
f =3D f * x;
x =3D x - 1;
};
return INT2NUM(f);
}=20

One nice thing about ruby is that the programmer does not have
to worry about supported-ranges for integer values. Ruby just
switches from "fixnum" objects into "bignum" objects, without
any attention from the programmer. It seems to me that the C
code that is listed above just assumes the multiplication of
'f * x' will not overflow. Is that the case?

--=20
Garance Alistair Drosehn =3D (e-mail address removed)

 

[Eric Hodel]

Checking out the writeup on Ruby2C at:

http://www.zenspider.com/~ryand/Ruby2C.pdf

there is one thing about the example on page 25 (of the pdf)
which concerns me a little bit. The example has:

class MyTest
def factorial(n)
f = 1
n.downto(2) { |x| f *= x }
return f
end
end

turn into:

static VALUE factorial(VALUE self,
VALUE _n) {
long n = NUM2INT(_n);
long f;
long x;
f = 1;
x = n;
while (x >= 2) {
f = f * x;
x = x - 1;
};
return INT2NUM(f);
}

One nice thing about ruby is that the programmer does not have
to worry about supported-ranges for integer values. Ruby just
switches from "fixnum" objects into "bignum" objects, without
any attention from the programmer. It seems to me that the C
code that is listed above just assumes the multiplication of
'f * x' will not overflow. Is that the case?

You are correct.

We could add the ability to automatically add the bignum/fixnum auto-
conversion stuff, but we've not needed the capability yet.

 

[Ryan Davis]

there is one thing about the example on page 25 (of the pdf)
which concerns me a little bit. The example has:

class MyTest
def factorial(n)
f = 1
n.downto(2) { |x| f *= x }
return f
end
end

turn into:

static VALUE factorial(VALUE self,
VALUE _n) {
long n = NUM2INT(_n);
long f;
long x;
f = 1;
x = n;
while (x >= 2) {
f = f * x;
x = x - 1;
};
return INT2NUM(f);
}

[cut]

I'm afraid that in your "concern" you missed the whole point of that
demonstration, which is:

OOOOO SHINY!

 

[Garance A Drosehn]

=20

=20
You are correct.
=20
We could add the ability to automatically add the bignum/fixnum
auto-conversion stuff, but we've not needed the capability yet.

It would be nice to at least detect that an overflow occurred, even
if you don't do the auto-conversion stuff. I do use ruby in some
situations simply because I don't want to have to think if I'm going
to be overflowing any fields that I'm collecting statistics into.

I do think the Ruby2C project could be quite useful, but I wouldn't
want to lose some of the more attractive characteristics of ruby
when taking advantage of it!

--=20
Garance Alistair Drosehn =3D (e-mail address removed)
Senior Systems Programmer or (e-mail address removed)
Rensselaer Polytechnic Institute; Troy, NY; USA