[6.2 🍒][C++Interop] Do not query C++ Standard Library Swift overlays when building Swift modules which were built without C++ interop #81912
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…tual modules which were not built with c++interop When the compiler is building a module without a defined formal C++ interop mode (e.g. building a textual interface which specifies it was built without C++ interop enabled), avoid looking up the C++ standard library Swift overlay for it. This is required for the case of the Darwin module, for example, which includes headers which map to C++ stdlib headers when the compiler is operating in C++ interop mode, but the C++ standard library Swift overlay module itself depends on 'Darwin', which results in a cycle. To resolve such situations, we can rely on the fact that Swift textual interfaces of modules which were not built with C++ interop must be able to build without importing the C++ standard library Swift overlay, so we avoid specifying it as a dependency for such modules. The primary source module, as well as Swift textual module dependencies which were built with C++ interop will continue getting a direct depedency of the 'CxxStdlib' Swift module. This was previously fixed in the dependency scanner for explicitly-built modules in swiftlang#81415.
artemcm
added
c++ interop
|
@swift-ci test |
Textual interfaces for 'Darwin' built with recent compilers specify that it is built witout C++ interop enabled. However, to ensure compatibility with versions of the 'Darwin' module built with older compilers, we hard-code this fact. This is required to break the module cycle that occurs when building the 'Darwin' module with C++ interop enabled, where the underlying 'Darwin' clang module depends on C++ standard library for which the compiler brings in the 'CxxStdlib' Swift overlay, which depends on 'Darwin'.
artemcm
force-pushed
the
FixImplicitBuildCXXInteropCycle_62
branch
from
ec16433 to
5749ef3
Compare
|
@swift-ci test |
nkcsgexi
approved these changes
Jun 2, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Cherry-pick of #81908
Explanation: Similarly to how this was fixed in [Dependency Scanning][C++Interop] Do not query
CxxStdlibSwift overlay for textual modules which were not built with c++interop #81415 in the Dependency Scanner for builds using Explicitly-Built modules, this change causes Implicitly-Built module code path to also forego querying Swift overlayCxxStdlibwhen the compiler is building a module with no declared "formal C++ interop mode".This change also temporarily hard-codes the
Darwinmodule to always have no formal C++ interop mode, for the sake of compatibility withDarwinSwift module textual interfaces which were constructed prior to the introduction of the-formal-cxx-interoperability-mode=option.Scope: Builds with C++Interop feature enabled which depend on the
Darwinmodule and other modules whose textual interfaces were originally built without C++Interop feature enabled.Risk: Low, this fix addresses the possibility (and actual presence) of a dependency cycle between Swift modules
DarwinandCxxStdlibby preventing query of C++ standard library Swift overlay when building Swift modules not built with C++Interop enabled, such asDarwin. Without this fix in place, theCxxStdlibSwift module textual interface cannot be built due to its dependency onDarwin, which pulls in C++ headers.Problem: rdar://151805687
Reviewed By: @cachemeifyoucan
Original PR: [C++Interop] Do not query C++ Standard Library Swift overlays when building Swift modules which were built without C++ interop #81908