[Lldb-commits] [lldb] [lldb] IRMemoryMap zero address mapping fix (PR #99045)

[Jason Molenda via lldb-commits]

jasonmolenda wrote:

I think we should change these checks to look for an explicitly inaccessible memory region, like 

```
       if (region_info.GetReadable() != MemoryRegionInfo::OptionalBool::eNo &&
            region_info.GetWritable() != MemoryRegionInfo::OptionalBool::eNo &&
            region_info.GetExecutable() !=
                MemoryRegionInfo::OptionalBool::eNo) {
           // This region is inaccessible, if it is large enough, use this address.
           if (ret + size < region_info.GetRange().GetRangeEnd())
            return ret;
           else 
             ret = region_info.GetRange().GetRangeEnd();
             // keep searching
```

and I also do think there is value in adding a special case for address 0.  Even if we have an inaddressable memory block at address 0 which should be eligible for shadowing with lldb's host memory, using that is a poor choice because people crash at address 0 all the time and we don't want references to that address finding the IRMemoryMap host side memory values.

```
        } else if (ret == 0) {
           // Don't put our host-side memory block at virtual address 0 even if it
           // seems eligible, we don't want to confuse things when a program 
           // crashes accessing that address, a common way of crashing.
           ret = region_info.GetRange().GetRangeEnd();
```



https://github.com/llvm/llvm-project/pull/99045