[Lldb-commits] [lldb] Make ValueObjectPrinter's handling of its ValueObject pointers more principled (NFC) (PR #81314)

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jimingham wrote:

Replying to a bunch of Greg's comments in sum.  

The way we use the ValueObjectPrinter is that you have a ValueObject and want to print it, so you make a ValueObjectPrinter passing in that ValueObject, then tell it to print it.  We don't preserve ValueObjectPrinters or try to reuse them.  There's no attempt to track changes in the ValueObject, for instance if you changed the use dynamic setting of the underlying ValueObject that won't effect the ValueObjectPrinter you made before you changed the setting.  It doesn't track the SyntheticChildProviderGeneration, so if you changed synthetic child providers on that ValueObject, it wouldn't track that, etc.

I think that's a useful simplification.   We don't have to reason about lifecycles in the ValueObjectPrinter.   The caller is responsible for the lifecycle of the ValueObject being printed - and that ValueObject's ClusterManager is responsible for all the children & synthetic children of that ValueObject.  The ValueObjectPrinter gets a reference to it because it expects to do some work on the ValueObject and then get discarded, which is how we always use it.

I can put in a comment to this effect, though the fact that we're taking in a `ValueObject &` and not a shared pointer also implies this is the way you are supposed to use it.




https://github.com/llvm/llvm-project/pull/81314