[libc++] Attempt to fix spurious modules-related failures in the CI
I'm not 100% sure what the issue actually is since I can't reproduce it
locally, however what I explain in the comment is my best attempt to
explain what's going on.
Differential Revision: https://reviews.llvm.org/D92131
diff --git a/libcxx/utils/libcxx/test/features.py b/libcxx/utils/libcxx/test/features.py
index 2f9a048..3023cae 100644
--- a/libcxx/utils/libcxx/test/features.py
+++ b/libcxx/utils/libcxx/test/features.py
@@ -40,7 +40,15 @@
Feature(name='has-fobjc-arc', when=lambda cfg: hasCompileFlag(cfg, '-xobjective-c++ -fobjc-arc') and
sys.platform.lower().strip() == 'darwin'), # TODO: this doesn't handle cross-compiling to Apple platforms.
Feature(name='objective-c++', when=lambda cfg: hasCompileFlag(cfg, '-xobjective-c++ -fobjc-arc')),
- Feature(name='modules-support', when=lambda cfg: hasCompileFlag(cfg, '-fmodules')),
+
+ # Note: We use a custom modules cache path to make sure that we don't reuse
+ # the default one, which can be shared across builds. This is important
+ # because we define macros in headers files, and a change in these macros
+ # doesn't seem to invalidate modules cache entries, which means we could
+ # build against now-invalid cached headers from a previous build.
+ Feature(name='modules-support',
+ when=lambda cfg: hasCompileFlag(cfg, '-fmodules'),
+ actions=lambda cfg: [AddCompileFlag('-fmodules-cache-path=%t/ModuleCache')]),
Feature(name='non-lockfree-atomics',
when=lambda cfg: sourceBuilds(cfg, """
