[clang][modules] Use file name as requested

[jansvoboda11]

This prevents redefinition errors due to having multiple paths for the same module map. (rdar://24116019)

Originally implemented and tested downstream by @bcardosolopes, I just made use of FileEntryRef::getNameAsRequested().

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-modules

Author: Jan Svoboda (jansvoboda11)

Changes

This prevents redefinition errors due to having multiple paths for the same module map. (rdar://24116019)

Originally implemented and tested downstream by @bcardosolopes, I just made use of FileEntryRef::getNameAsRequested().

---

Full diff: https://github.com/llvm/llvm-project/pull/68957.diff

4 Files Affected:

• (modified) clang/lib/Lex/HeaderSearch.cpp (+1-1)
• (modified) clang/lib/Serialization/ASTWriter.cpp (+2-2)
• (added) clang/test/Modules/Inputs/all-product-headers.yaml (+33)
• (added) clang/test/Modules/modulemap-collision.m (+15)

diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 4c8b64a374b47d5..cf1c0cc5284f316 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -1623,7 +1623,7 @@ bool HeaderSearch::findUsableModuleForHeader(
     ModuleMap::KnownHeader *SuggestedModule, bool IsSystemHeaderDir) {
   if (needModuleLookup(RequestingModule, SuggestedModule)) {
     // If there is a module that corresponds to this header, suggest it.
-    hasModuleMap(File.getName(), Root, IsSystemHeaderDir);
+    hasModuleMap(File.getNameAsRequested(), Root, IsSystemHeaderDir);
     return suggestModule(*this, File, RequestingModule, SuggestedModule);
   }
   return true;
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 27700c711d52fdd..0d216927d76260d 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1384,10 +1384,10 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
       SmallVector<FileEntryRef, 1> ModMaps(AdditionalModMaps->begin(),
                                            AdditionalModMaps->end());
       llvm::sort(ModMaps, [](FileEntryRef A, FileEntryRef B) {
-        return A.getName() < B.getName();
+        return A.getNameAsRequested() < B.getNameAsRequested();
       });
       for (FileEntryRef F : ModMaps)
-        AddPath(F.getName(), Record);
+        AddPath(F.getNameAsRequested(), Record);
     } else {
       Record.push_back(0);
     }
diff --git a/clang/test/Modules/Inputs/all-product-headers.yaml b/clang/test/Modules/Inputs/all-product-headers.yaml
new file mode 100644
index 000000000000000..53d683f2ad2ecc0
--- /dev/null
+++ b/clang/test/Modules/Inputs/all-product-headers.yaml
@@ -0,0 +1,33 @@
+{
+  'version': 0,
+  'case-sensitive': 'false',
+  'roots': [
+    {
+      'type': 'directory',
+      'name': "DUMMY_DIR/build/A.framework/PrivateHeaders"
+      'contents': [
+        {
+          'type': 'file',
+          'name': "A.h",
+          'external-contents': "DUMMY_DIR/sources/A.h"
+        }
+      ]
+    },
+    {
+      'type': 'directory',
+      'name': "DUMMY_DIR/build/A.framework/Modules"
+      'contents': [
+        {
+          'type': 'file',
+          'name': "module.modulemap",
+          'external-contents': "DUMMY_DIR/build/module.modulemap"
+        },
+        {
+          'type': 'file',
+          'name': "module.private.modulemap",
+          'external-contents': "DUMMY_DIR/build/module.private.modulemap"
+        }
+      ]
+    }
+  ]
+}
diff --git a/clang/test/Modules/modulemap-collision.m b/clang/test/Modules/modulemap-collision.m
new file mode 100644
index 000000000000000..5ada45da3dae191
--- /dev/null
+++ b/clang/test/Modules/modulemap-collision.m
@@ -0,0 +1,15 @@
+// REQUIRES: shell
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t/sources %t/build
+// RUN: echo "// A.h" > %t/sources/A.h
+// RUN: echo "framework module A {}" > %t/sources/module.modulemap
+// RUN: echo "framework module A.Private { umbrella header \"A.h\" }" > %t/sources/module.private.modulemap
+// RUN: cp %t/sources/module.modulemap %t/build/module.modulemap
+// RUN: cp %t/sources/module.private.modulemap %t/build/module.private.modulemap
+
+// RUN: sed -e "s:DUMMY_DIR:%t:g" %S/Inputs/all-product-headers.yaml > %t/build/all-product-headers.yaml
+// RUN: %clang_cc1 -fsyntax-only -ivfsoverlay %t/build/all-product-headers.yaml -F%t/build -fmodules -fimplicit-module-maps -Wno-private-module -fmodules-cache-path=%t/cache -x objective-c %s -verify
+
+// expected-no-diagnostics
+#import <A/A.h>

[benlangmuir]

How does this relate to the header search part of the change?

[jansvoboda11]

Yeah, this is a bit suspicious. This test started failing downstream after de85739 and this change appeared to be required to fix things.

Turns out llvm::SmallPtrSet<FileEntryRef, 1> determines equality of elements based on the equality of their void * representation, not based on FileEntryRef::operator==(). This means that when we find the module map through a VFS, but serialize the on-disk path, we aren't able to correctly match them together in ASTReader.

I don't want to go messing with the SmallPtrSet implementation, so I'll probably just revert D154905 (making the types unusable in SmallPtrSet) and switch from llvm::SmallPtrSet<FileEntryRef, 1> to llvm::DenseMap<FileEntryRef>.

[jansvoboda11]

Done in the two new commits.

[benlangmuir]

Thanks