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Restrict Weak-Re-Exports To @_exported Modules

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This code got refactored and it accidentally widened the applicable structures for this check. The idea is that you have the following structure

// Module A
@_weakLinked import B

// Module B
@_exported import C

And the compiler conspires to make it so the modules B AND C wind up weak-linked from module A.

The broadened check accidentally allowed the following:

// Module A
@_weakLinked import B

// Module B
import C // Oops!

Which caused quite a few more modules than were intended to be weak-linked. Restore the `Exported` filter to cut back on the amount of weak re-exports the compiler processes.

Resolves rdar://142706779
This commit is contained in:
Robert Widmann
2025-01-14 12:11:05 -07:00
parent fba8095144
commit 08940882c8
2 changed files with 31 additions and 1 deletions
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12
lib/AST/ImportCache.cpp
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@@ -428,7 +428,17 @@ ImportCache::getWeakImports(const ModuleDecl *mod) {
ModuleDecl *importedModule = import.module.importedModule;
result.insert(importedModule);
auto reexportedModules = getImportSet(importedModule).getAllImports();
// Only explicit re-exports of a weak-linked module are themselves
// weak-linked.
//
// // Module A
// @_weakLinked import B
//
// // Module B
// @_exported import C
SmallVector<ImportedModule, 4> reexportedModules;
importedModule->getImportedModules(
reexportedModules, ModuleDecl::ImportFilterKind::Exported);
for (auto reexportedModule : reexportedModules) {
result.insert(reexportedModule.importedModule);
}

20
test/IRGen/weaklinked_import_peer_transitive_objc.swift Normal file
View File

@@ -0,0 +1,20 @@
// REQUIRES: objc_interop, OS=macosx
// RUN: %empty-directory(%t)
//
// RUN: %target-swift-frontend -emit-module -emit-module-path %t/weaklinked_import_helper.swiftmodule -parse-as-library %S/Inputs/weaklinked_import_helper.swift -enable-library-evolution
//
// RUN: echo 'import Foundation' > %t/intermediate_foundation.swift
// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module -emit-module-path %t/intermediate_foundation.swiftmodule -parse-as-library %t/intermediate_foundation.swift -I %t -enable-library-evolution
//
// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -primary-file %s -I %t -emit-ir -Xcc -fmodule-map-file=%S/Inputs/weaklinked_import_helper_clang.modulemap | %FileCheck %s
@_weakLinked import intermediate_foundation
import Foundation
// ThisModule -weak imports-> intermediate_foundation -imports-> Foundation
// Because Foundation is _not_ re-exported, make sure any symbols from it are strongly referenced.
// CAUTION: Suppose you _want_ Foundation to be weak-linked. It's not enough to just `@_exported import Foundation`
// in the intermediate_foundation module. That only gets you the Swift half of the Foundation overlay.
// CHECK-DAG: @"OBJC_CLASS_$_NSNotification" = external global %objc_class
_ = NSNotification()