10 Apr
2022
10 Apr
'22
10:41 p.m.
On Sun, Apr 10, 2022 at 1:18 PM Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
wrote:
Unix had (and still may have, I'm not up on
Linux, etc) a really major,
hard
boundary beween 'user' code, in processes,and the kernel. There are
'instructions' that invoke system primitives - but not too many, and
limited
interactions across that boundary. So, restricted semantics.
The same is true for the more recent Unix variants, modulo a few special
cases such as Larry mentions, but broadly speaking userland and the kernel
are still separated.
Imagine building a
large application which had a hard boundary across the middle of it, with
extremely limited interactions across the boundary.
You mean like the Web? :-)
In 2000-2005 I wrote a substantial quasi-batch application that supported
$EMPLOYER's main product and was written about half in shell scripts and
half in Perl, or more accurately entirely in shell scripts, but if I needed
a pipeline component that wasn't already available in SunOS or as
third-party open source, I wrote it in Perl. (There was a single 10-line C
program to eliminate a performance bottleneck.) So the application as a
whole was full of hard boundaries across which nothing could pass except
text streams; I found that this added substantially to its debuggability
and maintainability.