[lldb-dev] [Bug 23299] New: transparent_pointers not working

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=23299

            Bug ID: 23299
           Summary: transparent_pointers not working
           Product: lldb
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: lldb-dev at cs.uiuc.edu
          Reporter: ribrdb at google.com
    Classification: Unclassified

While working on a LanguageRuntime plugin for go, I noticed some strangeness
with ValueObjects for pointers.
If I use valobj.GetChildMemberWithName(...), it returns a child, but with the
wrong address so the value is unusable.
However, if I use valobj.Dereference()->GetChildMemberWithName(...) I can read
the data.

I think I've tracked this down to an interaction between
ValueObject::GetPointerValue and ValueObjectChild::UpdateValue:
 - UpdateValue performs pointer arithmetic, saves the result in
m_value.GetScalar(), and sets the value type to an address (could be Host, Load
or FileAddress).
 - However, GetPointerValue only uses m_value if the value type is
eValueTypeScalar or eValueTypeVector.

So at least in the case where the offset is != 0, GetPointerValue seems to be
returning something wrong.
Simply changing the value type to scalar doesn't work, because other code is
expecting it to be some sort of address.

Unfortunately I haven't found a way to reproduce this using the public api so I
can't write a test for it.

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