[PATCH] D98291: [compiler-rt] Fix stale incremental builds when using `LLVM_BUILD_EXTERNAL_COMPILER_RT=ON`.

[Dan Liew via Phabricator via cfe-commits]

delcypher added a comment.

In D98291#2615590 <https://reviews.llvm.org/D98291#2615590>, @kubamracek wrote:

> When using Ninja, does this mean running a null build is no longer a null build, but it at least always invokes this sub-build? Not saying that's bad, just want to understand the change. What does the output of just "ninja" say in that case?

Yes the sub-build will always be invoked. That being said in the sub-build if nothing has changed it will be extremely fast because ninja is fast.

The output looks something like this

  $ ninja
  [0/3] Performing build step for 'compiler-rt'
  ninja: no work to do.
  [1/3] No install step for 'compiler-rt'
  [3/3] Completed 'compiler-rt'

This being said I'd expect very few people to actually run into this because this build configuration (`LLVM_BUILD_EXTERNAL_COMPILER_RT=ON`) is not common because it is not the default. The default if you enable compiler-rt is for it to be built as part of the main build using the host compiler, which is all kinds of wrong but is very convenient.

Swift does use this build configuration but I doubt anyone would complain about the extra console noise given how noisy build-script is.


Repository:
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  https://reviews.llvm.org/D98291/new/

https://reviews.llvm.org/D98291