I've got a small test solution with one exe and three Dlls, the exe calling the three Dlls once each. I've set the Build->Advanced->DLL Base Address setting to 0x41000000, 0x42000000 and 0x43000000 for Dll1.dll, Dll2.dll and Dll3.dll respectively. I've run
ngen install ConsoleApplication1.exe
and this has successfully ngen'd the application along with the three Dlls. I didn't really want to ngen the exe but so far this is the only way to produce any results at all.
At runtime I use VMMap to monitor the virtual address space and it reveals that the ngen'd Dlls are sitting within a consistant range of virtual memory, however they are still jumping around within that range, loading at a slightly differnt address every time I run them. VMMap reveals that there is nothing allocated at the addresses where I'm trying to load the images, so this jumpy behaviour is not being caused by address collisions.
I've been keeping logs:
Dll1 Dll2 Dll3
0x40140000 0x411D0000 0x42810000
0x40580000 0x41EB0000 0x426B0000
0x40190000 0x41FB0000 0x42380000
0x40F30000 0x41FD0000 0x42050000
0x409B0000 0x41BF0000 0x42910000
0x408E0000 0x41860000 0x42050000
0x40B50000 0x41280000 0x42A80000
Notice that the first two digits of the address remain consistant for all three Dlls across all runs.
My actual question: Is this an indicator of success? I'm a bit confused because I thought the Dlls were going to be sitting exactly at 0x41000000, 0x42000000 and 0x43000000. The results show that they hang around that area, but never actually sit where I asked them to sit. My understanding is that you want the Dlls to be loaded exactly at the address you ask them to so that they don't have to undergo the expensive rebasing operation (which is very very expensive when your Dlls have been ngen'd). But, isn't this exactly what's happening? Sure, my Dlls are hanging around in a certain area, but they aren't sitting exactly where I asked them to sit, so surely the expensive rebasing operation is being peformed at each run time? This is exactly what I wanted to avoid.
Note: I'm not interested in arguments for/against rebasing and ngen. I just want to know what's going on and how to get it working.
Cheers SO!
Could be ASLR (addres space layout randomization) - check out links from http://social.msdn.microsoft.com/Forums/en/vcgeneral/thread/bac7e300-f3df-4087-9c4b-847880d625ad