So<p>MSVC use PDB format which is undocumented.<p>LLVM want to implement PDB.<p>LLVM asks MS for help<p>MS disclose the portion of the MSVC code which deal with PDB<p>MS GitHub even says "Source code is the ultimate documentation :-)"<p>I think even the MS doesn't have formal documentation for PDB format.
This is very exciting. The blog post mentions cross-compilation, and being able to use lld should also result in faster link times and the ability to enable Clang features like CFI.<p>Congratulations on this milestone!