how to run the program only once (windows)

blueznl · Post by **blueznl** » Thu Nov 03, 2005 9:29 am

hmmm... does that mean datasection is always maintained in memory, or no, perhaps better put: does that mean that the address you pass from one program to another is valid and stays valid? i thought you couldn't rely on 'physical' adresses being the same to all programs... or is this ok these days on windows?

Dr. Dri · Post by **Dr. Dri** » Thu Nov 03, 2005 10:33 am

When you use adresses (for example a label) this adress refers to your process. So if it's the same program (what i know from the ExeFile) 2 identic adresses point to the same data.

I think this is "relative" adressing but i don't really know. :roll:
I don't know neither if you can get the physical adresses

Dri

blueznl · Post by **blueznl** » Thu Nov 03, 2005 2:00 pm

now let's up the challenge: let's create two DIFFERENT programs that need to access the same data

preferably by allocating a piece of fixed memory?

i've been looking through the win32 api and i'm pretty sure there must be some way, but haven't found it yet...

Post by **Dare2** » Thu Nov 03, 2005 2:21 pm

That's a good challenge.

Would FileMapping (CreateFileMapping, OpenFileMapping) be a way to go?

gnozal · Post by **gnozal** » Thu Nov 03, 2005 3:42 pm

There is already a userlib for this I think : GlobalSharedMemory (by Rings) http://pbosl.purearea.net/index.php?site=Libs . It uses file mapping IIRC.

blueznl · Post by **blueznl** » Thu Nov 03, 2005 6:58 pm

ha solved it

blueznl · Post by **blueznl** » Thu Nov 03, 2005 7:01 pm

it's also another alternative to check what program came first, just see if you can open a filemapping, if not there's no instance running yet

see here...

viewtopic.php?t=17542

PB · Post by PB » Thu Nov 03, 2005 10:30 pm

I still don't know what's wrong with the single-line sempahore example, it
works just fine for me with Win 98se, ME, 2K and XP. (I couldn't make it
fail under Win98se as reported here, maybe the steps to make it do so
could be posted so I can see for myself?).

Dr. Dri · Post by **Dr. Dri** » Fri Nov 04, 2005 10:13 am

@PB
I said i tried semaphore, mutex and if the program crash, the semaphore or the mutex still exists and you can't launch the program again.
That's what happenned to me (win98 se)

Dri

PB · Post by PB » Fri Nov 04, 2005 10:45 am

That's what I did too -- a sempahore under Win98se and I made the app
crash (by doing a GetClipboardText when the clipboard had >64K) and
I was still able to re-run it again, thus I believe the semphore died when
the app crashed. Anyway, that's my experience with it, and why I still
choose to use it to prevent multiple instances. <Shrugs>.

blueznl · Post by **blueznl** » Fri Nov 04, 2005 12:56 pm

an laternative may be a named pipe, playing with that now