Starting with 41e3919ded78d8870f7c95e9181c7f7e29aa3cc4 DiagnosticsEngine
creation might perform IO. It was implicitly defaulting to
getRealFileSystem. This patch makes it explicit by pushing the decision
making to callers.
It uses ambient VFS if one is available, and keeps using
`getRealFileSystem` if there aren't any VFS.
Make use of a physical copy, rather than real FS in unittests that
change working-directory to get rid of the side effect of changing cwd for the
whole process. It's triggering crashes depending on the test order.
Differential Revision: https://reviews.llvm.org/D152265
It was possible to re-add a module to a shared in-memory module cache
when search paths are changed. This can eventually cause a crash if the
original module is referenced after this occurs.
1. Module A depends on B
2. B exists in two paths C and D
3. First run only has C on the search path, finds A and B and loads
them
4. Second run adds D to the front of the search path. A is loaded and
contains a reference to the already compiled module from C. But
searching finds the module from D instead, causing a mismatch
5. B and the modules that depend on it are considered out of date and
thus rebuilt
6. The recompiled module A is added to the in-memory cache, freeing
the previously inserted one
This can never occur from a regular clang process, but is very easy to
do through the API - whether through the use of a shared case or just
running multiple compilations from a single `CompilerInstance`. Update
the compilation to return early if a module is already finalized so that
the pre-condition in the in-memory module cache holds.
Resolves rdar://78180255
Differential Revision: https://reviews.llvm.org/D105328
