PrintAsClang: Print #include for headers used from @cdecl functions

xymus · xymus · commit c0889d57c318 · 2025-05-14T16:04:37.000-07:00
Start printing `#include` for headers referenced from `@cdecl` function
signatures. This adds on top of the existing tiered imports. We already
print each module referenced from decls printed in the compatibility
header. Previously we printed mostly `@import` with an option to
fallback on a `#import`. This change adds a third fallback to `#include`
when the module is referenced from a `@cdecl` function signature. The
bridging header can also be imported in a similar way.
diff --git a/lib/PrintAsClang/PrintAsClang.cpp b/lib/PrintAsClang/PrintAsClang.cpp
@@ -409,7 +409,10 @@ writeImports(raw_ostream &out, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
              const FrontendOptions &frontendOpts,
              clang::HeaderSearch &clangHeaderSearchInfo,
              const llvm::StringMap<StringRef> &exposedModuleHeaderNames,
-             bool useCxxImport = false) {
+             bool useCxxImport = false,
+             bool useNonModularIncludes = false) {
+  useNonModularIncludes |= frontendOpts.EmitClangHeaderWithNonModularIncludes;
+
   // Note: we can't use has_feature(modules) as it's always enabled in C++20
   // mode.
   out << "#if __has_feature(objc_modules)\n";
@@ -446,7 +449,7 @@ writeImports(raw_ostream &out, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
   llvm::vfs::FileSystem &fileSystem = fileManager.getVirtualFileSystem();
   llvm::ErrorOr<std::string> cwd = fileSystem.getCurrentWorkingDirectory();
 
-  if (frontendOpts.EmitClangHeaderWithNonModularIncludes) {
+  if (useNonModularIncludes) {
     assert(cwd && "Access to current working directory required");
 
     for (auto searchDir = clangHeaderSearchInfo.search_dir_begin();
@@ -498,7 +501,7 @@ writeImports(raw_ostream &out, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
       }
       if (seenImports.insert(Name).second) {
         out << importDirective << ' ' << Name.str() << importDirectiveLineEnd;
-        if (frontendOpts.EmitClangHeaderWithNonModularIncludes) {
+        if (useNonModularIncludes) {
           if (const clang::Module *underlyingClangModule =
                   swiftModule->findUnderlyingClangModule()) {
             collectClangModuleHeaderIncludes(
@@ -521,19 +524,21 @@ writeImports(raw_ostream &out, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
       out << importDirective << ' ';
       ModuleDecl::ReverseFullNameIterator(clangModule).printForward(out);
       out << importDirectiveLineEnd;
-      if (frontendOpts.EmitClangHeaderWithNonModularIncludes) {
+      if (useNonModularIncludes) {
         collectClangModuleHeaderIncludes(
             clangModule, fileManager, requiredTextualIncludes, visitedModules,
             includeDirs, cwd.get());
       }
     }
   }
 
-  if (frontendOpts.EmitClangHeaderWithNonModularIncludes) {
-    out << "#else\n";
-    for (auto header : requiredTextualIncludes) {
+  if (useNonModularIncludes && !requiredTextualIncludes.empty()) {
+    out << "#elif defined(__OBJC__)\n";
+    for (auto header : requiredTextualIncludes)
       out << "#import <" << header << ">\n";
-    }
+    out << "#else\n";
+    for (auto header : requiredTextualIncludes)
+      out << "#include <" << header << ">\n";
   }
   out << "#endif\n\n";
   for (const auto header : textualIncludes) {
@@ -544,8 +549,13 @@ writeImports(raw_ostream &out, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
     if (bridgingHeader.empty())
       out << "#import <" << M.getName().str() << '/' << M.getName().str()
           << ".h>\n\n";
-    else
-      out << "#import \"" << bridgingHeader << "\"\n\n";
+    else {
+      out << "#if defined(__OBJC__)\n";
+      out << "#import \"" << bridgingHeader << "\"\n";
+      out << "#else\n";
+      out << "#include \"" << bridgingHeader << "\"\n";
+      out << "#endif\n\n";
+    }
   }
 }
 
@@ -606,17 +616,24 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
   writePrologue(os, M->getASTContext(), computeMacroGuard(M));
 
   // C content (@cdecl)
+  std::string moduleContentsScratch;
   if (M->getASTContext().LangOpts.hasFeature(Feature::CDecl)) {
     SmallPtrSet<ImportModuleTy, 8> imports;
-    emitExternC(os, [&] {
-      printModuleContentsAsC(os, imports, *M, interopContext);
-    });
+    llvm::raw_string_ostream cModuleContents{moduleContentsScratch};
+    printModuleContentsAsC(cModuleContents, imports, *M, interopContext);
+
+    llvm::StringMap<StringRef> exposedModuleHeaderNames;
+    writeImports(os, imports, *M, bridgingHeader, frontendOpts,
+                 clangHeaderSearchInfo, exposedModuleHeaderNames,
+                 /*useCxxImport=*/false, /*useNonModularIncludes*/true);
+
+    emitExternC(os, [&] { os << "\n" << cModuleContents.str(); });
+    moduleContentsScratch.clear();
   }
 
   // Objective-C content
   SmallPtrSet<ImportModuleTy, 8> imports;
-  std::string objcModuleContentsBuf;
-  llvm::raw_string_ostream objcModuleContents{objcModuleContentsBuf};
+  llvm::raw_string_ostream objcModuleContents{moduleContentsScratch};
   printModuleContentsAsObjC(objcModuleContents, imports, *M, interopContext);
   emitObjCConditional(os, [&] {
     llvm::StringMap<StringRef> exposedModuleHeaderNames;
diff --git a/test/PrintAsObjC/cdecl-includes-with-objc.swift b/test/PrintAsObjC/cdecl-includes-with-objc.swift
@@ -0,0 +1,82 @@
+/// Include module for use from both C and Objective-C @cdecl variants.
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t --leading-lines
+
+/// Generate the compatibility header cdecl.h
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) %t/Lib.swift \
+// RUN:   -emit-module -o %t -verify -F %t \
+// RUN:   -emit-clang-header-path %t/cdecl.h \
+// RUN:   -enable-experimental-feature CDecl
+
+/// Check compatibility header directly
+// RUN: %FileCheck %s --input-file %t/cdecl.h
+// RUN: %check-in-clang %t/cdecl.h -F %t
+// RUN: %check-in-clang-c %t/cdecl.h -F %t
+// RUN: %check-in-clang-cxx %t/cdecl.h -F %t
+
+// REQUIRES: swift_feature_CDecl
+// REQUIRES: objc_interop
+
+//--- CFramework.framework/Modules/module.modulemap
+
+framework module CFramework {
+    umbrella header "CFramework.h"
+}
+
+//--- CFramework.framework/Headers/CFramework.h
+
+typedef int IntFromCFramework;
+
+//--- Lib.swift
+
+import CFramework
+import CoreGraphics
+import Foundation
+
+// CHECK-NOT: Foundation;
+
+/// Imports for C variant to @_cdecl
+
+// CHECK: #if __has_feature(objc_modules)
+// CHECK: @import CFramework;
+// CHECK-NEXT: @import CoreGraphics;
+// CHECK-NEXT: #elif defined(__OBJC__)
+// CHECK-NEXT: #import <CFramework{{[/\\]}}CFramework.h>
+// CHECK-NEXT: #import <CoreGraphics.h>
+// CHECK-NEXT: #else
+// CHECK-NEXT: #include <CFramework{{[/\\]}}CFramework.h>
+// CHECK-NEXT: #include <CoreGraphics.h>
+// CHECK-NEXT: #endif
+
+// CHECK: #if defined(__cplusplus)
+// CHECK: extern "C" {
+// CHECK: #endif
+
+@cdecl("get_int_alias")
+public func getIntAlias() -> IntFromCFramework { 42 }
+// CHECK: SWIFT_EXTERN IntFromCFramework get_int_alias(void) SWIFT_NOEXCEPT SWIFT_WARN_UNUSED_RESULT;
+
+@cdecl("imports_cgpoint")
+public func importsCGPoint(pt: CGPoint) {  }
+// CHECK: SWIFT_EXTERN void imports_cgpoint(CGPoint pt) SWIFT_NOEXCEPT;
+
+// CHECK: #if defined(__cplusplus)
+// CHECK: } // extern "C"
+// CHECK: #endif
+
+/// Imports for Objective-C variant to @_cdecl
+
+@_cdecl("imports_cgpoint_objc")
+public func importsCGPointObjC(pt: CGPoint) {  }
+// CHECK: #if defined(__OBJC__)
+// CHECK: #if __has_feature(objc_modules)
+// CHECK-NEXT: #if __has_warning("-Watimport-in-framework-header")
+// CHECK-NEXT: #pragma clang diagnostic ignored "-Watimport-in-framework-header"
+// CHECK-NEXT: #endif
+// CHECK-NEXT: @import CoreGraphics;
+// CHECK-NEXT: #endif
+
+// CHECK: #if defined(__OBJC__)
+// CHECK: SWIFT_EXTERN void imports_cgpoint_objc(CGPoint pt) SWIFT_NOEXCEPT;
+// CHECK: #endif
diff --git a/test/PrintAsObjC/cdecl-includes.swift b/test/PrintAsObjC/cdecl-includes.swift
@@ -0,0 +1,110 @@
+/// Print #includes for C clients and reference imported types.
+/// This test shouldn't require the objc runtime.
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t --leading-lines
+
+/// Generate the compatibility header cdecl.h
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) %t/Lib.swift \
+// RUN:   -emit-module -verify -o %t -I %t \
+// RUN:   -import-bridging-header %t/BridgingHeader.h \
+// RUN:   -emit-clang-header-path %t/cdecl.h \
+// RUN:   -disable-objc-interop \
+// RUN:   -enable-experimental-feature CDecl
+
+/// Check compatibility header directly
+// RUN: %FileCheck %s --input-file %t/cdecl.h
+// RUN: %check-in-clang-c -I %t %t/cdecl.h \
+// RUN:   -isysroot %S/../Inputs/clang-importer-sdk
+
+/// Compile a client against the compatibility header
+// RUN: %clang-no-modules -c %t/Client.c -I %t -Werror \
+// RUN:   -isysroot %S/../Inputs/clang-importer-sdk
+
+// REQUIRES: swift_feature_CDecl
+
+//--- module.modulemap
+
+module CModule {
+    header "CModule_FileA.h"
+    header "sub/CModule_FileB.h"
+}
+
+//--- CModule_FileA.h
+
+struct CStruct { int a; };
+
+//--- sub/CModule_FileB.h
+
+union CUnion { long a; float b; };
+
+//--- Dependency.h
+
+typedef enum TKTimeSetting {
+    TKTimeSettingLight,
+    TKTimeSettingNormal,
+    TKTimeSettingDark
+} TKTimeSetting;
+
+//--- BridgingHeader.h
+
+#include "Dependency.h"
+
+//--- Lib.swift
+
+import CModule
+
+// CHECK: #if __has_feature(objc_modules)
+// CHECK: @import CModule;
+// CHECK-NEXT: #elif defined(__OBJC__)
+// CHECK-NEXT: #import <CModule_FileA.h>
+// CHECK-NEXT: #import <sub{{[/\\]}}CModule_FileB.h>
+// CHECK-NEXT: #else
+// CHECK-NEXT: #include <CModule_FileA.h>
+// CHECK-NEXT: #include <sub{{[/\\]}}CModule_FileB.h>
+// CHECK-NEXT: #endif
+
+// CHECK: #if defined(__OBJC__)
+// CHECK: #import "
+// CHECK-SAME: BridgingHeader.h"
+// CHECK-NEXT: #else
+// CHECK-NEXT: #include "
+// CHECK-SAME: BridgingHeader.h"
+// CHECK-NEXT: #endif
+
+// CHECK-NOT: BridgingHeader
+
+// CHECK: #if defined(__cplusplus)
+// CHECK: extern "C" {
+// CHECK: #endif
+
+@cdecl("mirror_struct")
+public func a_mirrorStruct(_ a: CStruct) -> CStruct { a }
+// CHECK: SWIFT_EXTERN struct CStruct mirror_struct(struct CStruct a) SWIFT_NOEXCEPT SWIFT_WARN_UNUSED_RESULT;
+
+@cdecl("mirror_union")
+public func b_mirrorStruct(_ a: CUnion) -> CUnion { a }
+// CHECK: SWIFT_EXTERN union CUnion mirror_union(union CUnion a) SWIFT_NOEXCEPT SWIFT_WARN_UNUSED_RESULT;
+
+
+@cdecl("TKGetDefaultToastSetting")
+public func c_defaultToastSetting() -> TKTimeSetting { TKTimeSettingNormal } // It would be nice to import TKTimeSettingNormal as a member.
+// CHECK: SWIFT_EXTERN TKTimeSetting TKGetDefaultToastSetting(void) SWIFT_NOEXCEPT SWIFT_WARN_UNUSED_RESULT;
+
+// CHECK:      #if defined(__cplusplus)
+// CHECK-NEXT: }
+// CHECK-NEXT: #endif
+
+//--- Client.c
+
+#include "cdecl.h"
+
+int main() {
+  struct CStruct s = { 42 };
+  struct CStruct s_out = mirror_struct(s);
+
+  union CUnion u = { 43 };
+  union CUnion u_out = mirror_union(u);
+
+  TKTimeSetting def = TKGetDefaultToastSetting();
+}
