13 May
2024
13 May
'24
4:56 a.m.
On Sun, May 12, 2024 at 4:14 PM John Levine <johnl(a)taugh.com> wrote:
It appears that Larry McVoy <lm(a)mcvoy.com>
said:
Perhaps, but as I've written here before, `fork`/`exec` vs `spawn` is
a false dichotomy. Another alternative is a `proccreate`/`procrun`
pair, the former of which creates an unrunnable process, the latter of
which marks it runnable. Coupled with a set of primitives to
manipulate the state of an extant, but unrunnable, process and you
have the advantages of fork/exec without the downsides (which are
well-known;
https://www.microsoft.com/en-us/research/uploads/prod/2019/04/fork-hotos19.…)
Similarly, this gives you the functionality of spawn, without the
downside of a singularly complicated interface. Could you have
implemented that in something as small as the PDP-7? Perhaps not, but
it does not follow that `fork` now remains a good primitive.
My spelunking in the original GENIE documentation leads me to believe
that its `fork` provided functionality similar to what I described.
- Dan C.
Perhaps a meaningless aside, but I agree on
fork(). In the last major
project I did, which was cross platform {windows,macos, all the major
Unices, Linux}, we adopted spawn() rather than fork/exec. There is no way
(that I know of) to fake fork() on Windows but it's easy to fake spawn().
The whole point of fork() is that it lets you get the effect of spawn with
a lot less internal mechanism. Spawn is equivalent to:
fork()
... do stuff to files and environment ...
exec()
By separating the fork and the exec, they didn't have to put all of
the stuff in the 12 paragraphs in the spawn() man page into the the
tiny PDP-11 kernel.