[PATCH] D42326: [COFF] add option to avoid overwriting unchanged import libraries

[Zachary Turner via Phabricator via llvm-commits]

zturner added a comment.

In https://reviews.llvm.org/D42326#982664, @inglorion wrote:

> 2. Enabling the new functionality by default. I did not consider this safe to do, because it breaks the assumptions many people and build systems make about how things work. If A depends on B and B depends on C, then, without the change, changing C will cause A and B to be rebuilt and receive new timestamps. With the change, if rebuilding B results in the same bytes that were already in there, B will retain its old timestamp and A will not be rebuilt. This also means that B will now look older than C. This seems like an unexpected enough change in semantics that I would want people to explicitly opt into it.


We should do by default whatever MSVC does by default.  Can you do a few simple tests with MSVC and just mimic exactly what they do in every case?


https://reviews.llvm.org/D42326