ARM9MemoryBus::UpdateMemoryMap tries to access invalid memory

[ghost]

The sequence of events is:

1. ARM9MemoryBus constructor
2. UpdateMemoryMap(0, 0x100000000ULL);
3. case 0x06: table[index] = VisitVRAMByAddress<GetUnsafePointerFunctor>(address);
4. GetUnsafePointerFunctor
5. GetUnsafePointer

At the first attempt to read an address above the 0x068A3FFF mark (VRAM 656KB limit) everything blows up.
Could fix it checking before calling VisitVRAMByAddress:

case 0x06: {
if ((address & 0xFFFFF) < 0xa4000) //Check
table[index] = VisitVRAMByAddress<GetUnsafePointerFunctor<u8>>(address);
break;
}

But for current lack of whole design complete understanding and fleroviux intentions, I'm just documenting here and not opening a pull request.

Tested on:

Platform: Win10
Compiler: Clang 11 under MSVCRT (MSVC can't handle the metaprogramming and won't build, at least in the current stable 14.29)
(logically should be an issue in other platforms, logically)

[fleroviux]

Can you confirm that this is fixed as of the latest commit 094361c?

The problem was in the vram.hpp file, it defined LCDC VRAM as a region with 41 pages but mask is 63.
This correctly models the mirroring behavior of LCDC VRAM but the Region class template didn't account for the mask >= number of pages case. To avoid a branch I just made the LCDC region 64 pages large, which is still correct, just slightly more wasteful.

[ghost]

I knew you would come with a better solution ヾ(≧▽≦*)o
Merged upstream and now works without a flaw! Now it can compile and run without problems under clang+Visual Studio on Windows.