On Friday, 24 May 2013 at 09:56:25 UTC, Diggory wrote:
I'm fairly sure windows only shares memory between instances of
the same DLL, not executables.
Oh? I thought Windows treats all modules in the same way. Do you
have a source?
You're still executing part of the user's code and it's going
to be exceedingly hard to satisfactorily explain why the main
function will be called twice except the second time it will
mysteriously stop half-way through because the runtime init
function doesn't return...
I don't see that as a problem, considering such a GC would need
to be opt-in.
Any security software with the active defense type stuff,
Commodo does it for example. The things they ask you about vary
and it's completely pointless IMO, but they do ask for
permission for practically everything and with two processes
that's twice as much to ask you about.
The reason why I asked for a specific example is that I don't
know of any actual case when this will be a problem in practice.
For one, I've never seen security software that reacts
differently on two instances of the same executable - usually,
any permissions you set are for the .exe file, or more generic
rules (like port numbers).
For two, the satellite process does not need any kinds of
permissions. Even the requirement of accessing other processes'
memory that the straight-forward approach needs can be avoided by
allowing the satellite process to inherit a handle to the main
process.
Anyway, my main point is that it's not the kind of thing you
want to impose as standard on all D applications, there may be
other problems it causes depending on what the program is for.
If it exists at all it should be opt-in and the default should
still be as performant as possible.
Yes, which is why I also think it should be opt-in.
I've tried writing a generational GC for D that used page
protection for write barriers a while ago. IIRC, I ran into
performance issues (the page faults were rather expensive).
Hmm, it shouldn't really be much slower than the technique
Leandro was using - both rely on the exact same number of page
faults - and his results looked very promising.
Leandro wasn't using Windows ;)
