[Lldb-commits] [PATCH] D59485: [ASTImporter] Add an ImportInternal method to allow customizing Import behavior.

Gabor Marton via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Fri Mar 22 03:52:31 PDT 2019

martong added a comment.

> @martong It's not related to lookup or anything like that, it's just that we don't have enough information in our debug info AST to allow people to use meta programming. The custom logic we have in LLDB looks into the std C++ module to fill out these gaps in the AST by hand when they are used in an expression.
> The remark about the alternative being slow just means that fixing all the templates we have in our debug info AST seems like a costly approach. I'm also not sure how well it would work, as I never tried mixing a C++ module in an ASTContext that isn't currently being parsed by Clang.

Well, I still don't understand how LLDB synthesis the AST. 
So you have a C++ module in a .pcm file. This means you could create an AST from that with ASTReader from it's .clang_ast section, right? In that case the AST should be complete with all type information. If this was the case then I don't see why it is not possible to use clang::ASTImporter to import templates and specializations, since we do exactly that in CTU.

Or do you guys create the AST from the debug info, from the .debug_info section of .pcm module file? And this is why AST is incomplete? I've got this from https://www.youtube.com/watch?v=EgkZ8PTNSHQ&list=PL85Cf-ok7HpppFWlp2wX_-A1dkyFVlaEB&index=2&t=5s
If this is the case, then comes my naiive quiestion: Why don't you use the ASTReader?



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