[cmucl-imp] Snapshot 2015-06

[Stelian Ionescu]

> On Fri, Jun 12, 2015 at 6:52 AM, Stelian Ionescu <sionescu at cddr.org>
> wrote:
> 
> > You can have both, which IMO is the right thing wrt. to
> > backwards-compatibility with C programs.
> >
> 
> Interesting.  But, how exactly would this work?  The C library provides
> no
> signal to invalidate a cache when its copy of the environment changes  As
> such, it seems impossible to efficiently keep a copy of the environment
> in
> Lisp consistent.  Without consistency, I am not sure how backward
> compatibility is maintained.

There is no "its copy", just a single array that putenv() changes
destructively. During an exec(), the runtime linker allocates that
array, having a fixed maximum size baked in the kernel, at a fixed
offset in the process address space. If something modifies that in-place
and screws it up, there's no backup.

 
> > With IOlib one can query the process-level environment or turn that into
> > an object, manipulate it and pass it to CREATE-PROCESS. See
> > https://github.com/sionescu/iolib/blob/master/src/os/os-unix.lisp#L10.
> >
> 
> Thanks for the pointer.  I noticed that your hash-table construction does
> not check for the preexistence of a value when doing inserts from the
> environment list (on line 101).  While uncommon, this nevertheless is a
> discrepancy between the behavior of getenv in your library and the and
> getenv in the C library.  This can create a security issue.

Thanks for the notice. I opened
https://github.com/sionescu/iolib/issues/24

-- 
Stelian Ionescu a.k.a. fe[nl]ix
Quidquid latine dictum sit, altum videtur.
http://common-lisp.net/project/iolib