The algorithm already performs pairwise checks on module dependencies brought into compilation per-source-file. Previously, the algorithm considered the entire sub-graph of a given source file. Actual source compiles do not consider the full transitive module dependency set for cross-import-overlay lookup, but rather only directly-imported modules in a given source file, and '@_exported import' Swift transitive dependencies.
This change adds tracking of whether a given import statement is 'exported' to the dependency scanner and then refines the cross-import overlay lookup logic to only consider transitive modules that are exported by directly-imported dependencies.
Instead, only add the overlay itself, and let it refer to its own dependencies, which will still get recorded in the overall output.
Resolves rdar://117010118
We should hold off actually building the binary module file until it is imported.
`canImport` queries can happen, for example, during dependency scanning, when we do not wish to have the scanner tool execute any module builds.
Resolves rdar://82603098
Before this change, we always use the Swift target triple to instantiate the internal
Clang instance. When loading a Swift module from the textual interface, we may pick up
a lower target triple to use to build the Swift module because the target is hard-coded
in the textual interface file. This implies we may end up building multiple versions of the
same Clang module, one for each target triple of the loading Swift module.
This change adds a new frontend flag -clang-target to allow clients to specify a
consistent clang target to use across the Swift module boundaries. This value won't change
because it's not part of .swiftinterface files.
swift-driver should pass down -clang-target for each frontend invocation, and its value should be
identical to -target.
Related to: rdar://72480261
To support -disable-implicit-swift-modules, the explicitly built modules
are passed down as compiler arguments. We need this new module loader to
handle these modules.
This patch also stops ModuleInterfaceLoader from building module from interface
when -disable-implicit-swift-modules is set.
Additional flags in interface files may change parsing behavior like #if
statements. We should use a fresh ASTContext with these additional
flags when parsing interface files to collect imports.
rdar://62612027
When there is a bridging header associated with the module, scan and record
its dependencies. Note them in a separate structure to capture the specific
dependencies of the bridging header.
Implement a new "fast" dependency scanning option,
`-scan-dependencies`, in the Swift frontend that determines all
of the source file and module dependencies for a given set of
Swift sources. It covers four forms of modules:
1) Swift (serialized) module files, by reading the module header
2) Swift interface files, by parsing the source code to find imports
3) Swift source modules, by parsing the source code to find imports
4) Clang modules, using Clang's fast dependency scanning tool
A single `-scan-dependencies` operation maps out the full
dependency graph for the given Swift source files, including all
of the Swift and Clang modules that may need to be built, such
that all of the work can be scheduled up front by the Swift
driver or any other build system that understands this
option. The dependency graph is emitted as JSON, which can be
consumed by these other tools.
