[PATCH] D94639: [DebugInfo][CodeView] Change in line tables only mode to emit parent/context scopes for functions, using declarations for types

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

In D94639#2917340 <https://reviews.llvm.org/D94639#2917340>, @SeTSeR wrote:

> Hello! As far as I understand, Clang does not preserve info about namespace for functions declared in namespaces with `-gline-numbers-only` flag. Is there any way to retrieve this info for DWARF? I thought FIXME at line 261 in CGDebugInfo was addressing exactly this issue.

No, I don't think there is a way to achieve this.

The current -gcodeview -gline-tables-only behavior as I understand it is to emit regular debug info, but skip two key source of info:

- never emit complete class declarations, always use forward decls
- never emit variable locations, only emit source locations

For DWARF, I think we also try to skip namespace scopes, class forward decls, function types, and other things like that, but I forget the details.

I happen to know that many users of -gline-tables-only are very space constrained: we can't simply port this change from CV to DWARF. We'd have to add a new flag. The bar for such a flag is high. If someone provides a well-motivated use case, we could consider it.


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