Re: gh_enter reconsidered

[Maciej Stachowiak <mstachow@mit.edu>]

jj@lcs.mit.edu writes:
> 
> Since I claimed the Boehm collector already went through the trouble
> of finding the start of the stack on many architectures, I decided to
> see how.
> 
> http://reality.sgi.com/employees/boehm_mti/gc_source/gc.tar.Z
> 
> From config.h:
> 
> /*
>  * For each architecture and OS, the following need to be defined:
>  *

Did your message get cut off? In any case, I looked at that file, and
the stack bottom seems to be found for most unixen via an OS and
hardware specific hardwired constant. I don't think that's a good way
to do it. Other methods include taking the address of errno (allegedly
works on AIX, already in my [posted in another thread] file of tests),
or using assembly code. Of course, the Boehm code needs to find the
_absolute_ top of the stack when possible, while Guile can get away
with anything closer to the stack bottom than main()'s frame pointer
is.

The environ hack, ugly as it is, is IMO cleaner than
platform-dependent constants.

 - Maciej