2012-06-21

apply argument limit

It was yesterday evening I was considering that values might have to be implemented not to allocate any memory such as mosh or Gauche. (well, currently values returns first class object named values too).

Then I wrote test code like this;
(import (rnrs) (srfi :42))
(apply values (list-ec (: x 150000) (* x x)))
Well, it just applies a list contains 150000 elements to values. I don't know why I put such a huge number but it revealed a bug in Sagittarius. (could be mosh as well).

The problem is really simple. Sagittarius' compiler compiles apply procedure as a builtin instruction APPLY. This instruction pushes given arguments to stack, however it does not check whether or not stack overflows and current maximum stack size is 10000.Yes, it breaks something I don't want to.

The solution can be 2 ways. The easiest way is check arguments count and if it's more than maximum then raises an error. The not so easy way is change the behaviour of APPLY a bit.

The first one is a bit awkward even if nobody applies such huge number of arguments. So I will do the latter one.

I don't know when I can say it's stable...

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