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Always weak-link symbols from the concurrency library when back-deploying #40007

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Merged
merged 1 commit into from
Nov 2, 2021
Merged

Always weak-link symbols from the concurrency library when back-deploying #40007

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12 changes: 11 additions & 1 deletion lib/AST/Decl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -871,8 +871,18 @@ bool Decl::isStdlibDecl() const {
AvailabilityContext Decl::getAvailabilityForLinkage() const {
auto containingContext =
AvailabilityInference::annotatedAvailableRange(this, getASTContext());
if (containingContext.hasValue())
if (containingContext.hasValue()) {
// If this entity comes from the concurrency module, adjust it's
// availability for linkage purposes up to Swift 5.5, so that we use
// weak references any time we reference those symbols when back-deploying
// concurrency.
ASTContext &ctx = getASTContext();
if (getModuleContext()->getName() == ctx.Id_Concurrency) {
containingContext->intersectWith(ctx.getConcurrencyAvailability());
}

return *containingContext;
}

if (auto *accessor = dyn_cast<AccessorDecl>(this))
return accessor->getStorage()->getAvailabilityForLinkage();
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23 changes: 23 additions & 0 deletions test/Concurrency/Backdeploy/weak_linking.swift
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@@ -0,0 +1,23 @@
// RUN: %empty-directory(%t)
// RUN: %target-swift-frontend %s -target x86_64-apple-macosx12.0 -module-name main -emit-ir -o %t/new.ir
// RUN: %FileCheck %s --check-prefix=NEW < %t/new.ir
// RUN: %target-swift-frontend %s -target x86_64-apple-macosx10.15 -module-name main -emit-ir -o %t/old.ir -disable-availability-checking
// RUN: %FileCheck %s --check-prefix=OLD < %t/old.ir

// REQUIRES: OS=macosx

// NEW-NOT: extern_weak
// OLD: @"$sScPMn" = extern_weak global
// OLD: declare extern_weak swiftcc i8* @swift_task_alloc
// OLD: declare extern_weak swiftcc %swift.metadata_response @"$sScPMa"
// OLD: declare extern_weak swiftcc i8 @"$sScP8rawValues5UInt8Vvg"

@available(macOS 12.0, *)
public func g() async -> String { "hello" }

@available(macOS 12.0, *)
public func f() async {
Task {
print(await g())
}
}