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It is possible for a module interface (e.g., ModuleA) to be generated with C++ interop disabled, and then rebuilt with C++ interop enabled (e.g., because ModuleB, which imports ModuleA, has C++ interop enabled). This circumstance can lead to various issues when name lookup behaves differently depending on whether C++ interop is enabled, e.g., when a module name is shadowed by a namespace of the same name---this only happens in C++ because namespaces do not exist in C. Unfortunately, naming namespaces the same as a module is a common C++ convention, leading to many textual interfaces whose fully-qualified identifiers (e.g., c_module.c_member) cannot be correctly resolved when C++ interop is enabled (because c_module is shadowed by a namespace of the same name). This patch does two things. First, it introduces a new frontend flag, -formal-cxx-interoperability-mode, which records the C++ interop mode a module interface was originally compiled with. Doing so allows subsequent consumers of that interface to interpret it according to the formal C++ interop mode. Note that the actual "versioning" used by this flag is very crude: "off" means disabled, and "swift-6" means enabled. This is done to be compatible with C++ interop compat versioning scheme, which seems to produce some invalid (but unused) version numbers. The versioning scheme for both the formal and actual C++ interop modes should be clarified and fixed in a subsequent patch. The second thing this patch does is fix the module/namespace collision issue in module interface files. It uses the formal C++ interop mode to determine whether it should resolve C++-only decls during name lookup. For now, the fix is very minimal and conservative: it only filters out C++ namespaces during unqualified name lookup in an interface that was originally generated without C++ interop. Doing so should fix the issue while minimizing the chance for collateral breakge. More cases other than C++ namespaces should be added in subsequent patches, with sufficient testing and careful consideration. rdar://144566922
58 lines
2.4 KiB
Swift
58 lines
2.4 KiB
Swift
// RUN: %empty-directory(%t)
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// RUN: %empty-directory(%t/include)
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// RUN: split-file %s %t
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// Generate textual interface for shim.swift without C++ interop enabled, then
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// re-compile it with C++ interop enabled (because it is used by program.swift,
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// which is compiled with C++ interop enabled).
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//
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// RUN: %empty-directory(%t/lib)
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// RUN: %target-swift-emit-module-interface(%t/lib/shim.swiftinterface) %t/shim.swift -module-name shim -I %t/include
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// RUN: %FileCheck %t/shim.swift < %t/lib/shim.swiftinterface
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// RUN: %target-swift-frontend %t/program.swift -typecheck -verify -cxx-interoperability-mode=default -I %t/include -I %t/lib
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//--- include/module.modulemap
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// A Clang module which will first be compiled in C mode, and then later compiled in C++ mode
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module c2cxx {
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header "c2cxx.h"
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export *
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}
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//--- include/c2cxx.h
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// A header file that defines a namespace with the same name as the module,
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// a common C++ idiom. We want to make sure that it does not shadow the module
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// in textual interfaces generated with C++ interop disabled, but later compiled
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// with C++ interop enabled.
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#ifndef __C2CXX_NAMESPACE_H
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#define __C2CXX_NAMESPACE_H
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typedef int c2cxx_number; // always available and resilient
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#ifdef __cplusplus
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namespace c2cxx { typedef c2cxx_number number; }; // only available in C++
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#endif // __cplusplus
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#endif // __C2CXX_NAMESPACE_H
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//--- shim.swift
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// A shim around c2cxx that exposes a c2cxx decl in its module interface
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import c2cxx
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// Exposes a (fully-qualified) c2cxx decl in its module interface.
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public func shimId(_ n: c2cxx_number) -> c2cxx_number { return n }
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// CHECK: public func shimId(_ n: c2cxx.c2cxx_number) -> c2cxx.c2cxx_number
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// ^^^^^`- refers to the module
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// @inlinable functions have their bodies splatted in the module interface file;
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// those verbatim bodies may contain unqualified names.
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@inlinable public func shimIdInline(_ n: c2cxx_number) -> c2cxx_number {
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// CHECK: public func shimIdInline(_ n: c2cxx.c2cxx_number) -> c2cxx.c2cxx_number
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// ^^^^^`- refers to the module
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let m: c2cxx_number = n
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// CHECK: let m: c2cxx_number = n
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// ^^^^^^^^^^^^`- verbatim (unqualified)
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return m
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}
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//--- program.swift
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// Uses the shim and causes it to be (re)built from its interface
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import shim
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func numberwang() { let _ = shimId(42) + shimIdInline(24) }
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