[PATCH] D79671: [MsgPack] MsgPackDocument::readFromBlob now merges

[Tim Renouf via Phabricator via llvm-commits]

tpr marked an inline comment as done.
tpr added inline comments.


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Comment at: llvm/include/llvm/BinaryFormat/MsgPackDocument.h:370-371
+          Merger = [](DocNode *DestNode, DocNode SrcNode, DocNode MapKey) {
+            return (DestNode->isMap() && SrcNode.isMap()) ||
+                   (DestNode->isArray() && SrcNode.isArray());
+          });
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foad wrote:
> tpr wrote:
> > foad wrote:
> > > Can't the body of this default merger be just `llvm_unreachable();`?
> > Probably, although that is a change in behavior from before, which I'd rather not do as I think I am not the only user of it. (Also, even if we did do that, it should be "return false" so that the readFromBlob call returns false for failure.)
> I don't get it. Surely in existing use cases, DestNode is nil so the merger will not be called. And if it *was* called, there's no point in it returning true unless it actually copies some data from SrcNode to DestNode, otherwise it'll claim to have done a merge but actually it ignored the new incoming data and left the document exactly as it was (i.e. empty). What am I missing?
It's a bit of a corner case, but, in the code before, I think you could have a map containing two entries of the same name, both maps, and it would merge them together. Having two entries of the same name is probably not legal MsgPack in some sense.


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  https://reviews.llvm.org/D79671/new/

https://reviews.llvm.org/D79671