[clang-tools-extra] ff5363b - [clangd][remote] Add clangd-index-server support for cross platform indexes (#207202)

[via cfe-commits]

Author: Bartosz Wiklak
Date: 2026-07-10T17:34:56+03:00
New Revision: ff5363bf29ba9f426b241abb9e72d12d9b785221

URL: https://github.com/llvm/llvm-project/commit/ff5363bf29ba9f426b241abb9e72d12d9b785221
DIFF: https://github.com/llvm/llvm-project/commit/ff5363bf29ba9f426b241abb9e72d12d9b785221.diff

LOG: [clangd][remote] Add clangd-index-server support for cross platform indexes (#207202)

The main use case is to serve windows index on linux server. 

Without this change server wasn't able to check if project_root path is
absolute and was closed with error: "Index root should be an absolute
path."

This change is meant to solve issue:
https://github.com/clangd/clangd/issues/2646

Added: 
    clang-tools-extra/clangd/test/remote-index/cross-platform-root.test

Modified: 
    clang-tools-extra/clangd/index/remote/marshalling/Marshalling.cpp
    clang-tools-extra/clangd/index/remote/server/Server.cpp
    clang-tools-extra/clangd/unittests/remote/MarshallingTests.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clangd/index/remote/marshalling/Marshalling.cpp b/clang-tools-extra/clangd/index/remote/marshalling/Marshalling.cpp
index aa607926a6d51..903583414dd43 100644
--- a/clang-tools-extra/clangd/index/remote/marshalling/Marshalling.cpp
+++ b/clang-tools-extra/clangd/index/remote/marshalling/Marshalling.cpp
@@ -59,14 +59,16 @@ Marshaller::Marshaller(llvm::StringRef RemoteIndexRoot,
     : Strings(Arena) {
   llvm::StringRef PosixSeparator = get_separator(Style::posix);
   if (!RemoteIndexRoot.empty()) {
-    assert(is_absolute(RemoteIndexRoot));
+    assert(is_absolute(RemoteIndexRoot, Style::posix) ||
+           is_absolute(RemoteIndexRoot, Style::windows));
     this->RemoteIndexRoot = convert_to_slash(RemoteIndexRoot, Style::windows);
     llvm::StringRef Path(this->RemoteIndexRoot);
     if (!is_separator(this->RemoteIndexRoot.back(), Style::posix))
       this->RemoteIndexRoot += PosixSeparator;
   }
   if (!LocalIndexRoot.empty()) {
-    assert(is_absolute(LocalIndexRoot));
+    assert(is_absolute(LocalIndexRoot, Style::posix) ||
+           is_absolute(LocalIndexRoot, Style::windows));
     this->LocalIndexRoot = convert_to_slash(LocalIndexRoot, Style::windows);
     llvm::StringRef Path(this->LocalIndexRoot);
     if (!is_separator(this->LocalIndexRoot.back(), Style::posix))

diff  --git a/clang-tools-extra/clangd/index/remote/server/Server.cpp b/clang-tools-extra/clangd/index/remote/server/Server.cpp
index 87e4c2d938e63..f24e21ef0fdae 100644
--- a/clang-tools-extra/clangd/index/remote/server/Server.cpp
+++ b/clang-tools-extra/clangd/index/remote/server/Server.cpp
@@ -589,7 +589,9 @@ int main(int argc, char *argv[]) {
   llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
   llvm::sys::SetInterruptFunction(&clang::clangd::requestShutdown);
 
-  if (!llvm::sys::path::is_absolute(IndexRoot)) {
+  if (!llvm::sys::path::is_absolute(IndexRoot, llvm::sys::path::Style::posix) &&
+      !llvm::sys::path::is_absolute(IndexRoot,
+                                    llvm::sys::path::Style::windows)) {
     llvm::errs() << "Index root should be an absolute path.\n";
     return -1;
   }

diff  --git a/clang-tools-extra/clangd/test/remote-index/cross-platform-root.test b/clang-tools-extra/clangd/test/remote-index/cross-platform-root.test
new file mode 100644
index 0000000000000..08fa237f576fe
--- /dev/null
+++ b/clang-tools-extra/clangd/test/remote-index/cross-platform-root.test
@@ -0,0 +1,8 @@
+# Verify that clangd-index-server accepts Windows-style absolute paths as
+# project root, allowing the server to run on Linux with a Windows-built index.
+# "C:/project" is absolute in Windows style but not POSIX style.
+# REQUIRES: clangd-remote-index
+# RUN: not clangd-index-server --server-address=localhost:0 %t.idx "C:\\project" 2>&1 | FileCheck %s
+# The server should pass the path validation and fail later on missing index.
+# CHECK-NOT: Index root should be an absolute path
+# CHECK: does not exist

diff  --git a/clang-tools-extra/clangd/unittests/remote/MarshallingTests.cpp b/clang-tools-extra/clangd/unittests/remote/MarshallingTests.cpp
index 85e79eae331bc..fe0dc4a67622c 100644
--- a/clang-tools-extra/clangd/unittests/remote/MarshallingTests.cpp
+++ b/clang-tools-extra/clangd/unittests/remote/MarshallingTests.cpp
@@ -449,6 +449,44 @@ TEST(RemoteMarshallingTest, URIToRelativePathTranslation) {
   llvm::consumeError(RelativePath.takeError());
 }
 
+TEST(RemoteMarshallingTest, CrossPlatformPathsRoundTrip) {
+  llvm::BumpPtrAllocator Arena;
+  llvm::UniqueStringSaver Strings(Arena);
+
+  // Simulate a Windows-built index.
+  llvm::StringRef RemoteIndexRoot = "C:\\remote\\project\\";
+  Marshaller ProtobufMarshaller(RemoteIndexRoot, testPath("local/project/"));
+
+  clangd::Ref Ref;
+  Ref.Kind = clangd::RefKind::Declaration;
+  clangd::SymbolLocation Location;
+  Location.Start.setLine(1);
+  Location.Start.setColumn(2);
+  Location.End.setLine(3);
+  Location.End.setColumn(4);
+  // Construct the URI as a Windows machine would have serialized it into the
+  // index: file:///C:/remote/project/lib/File.cpp.
+  Location.FileURI =
+      Strings
+          .save("file:///" +
+                convert_to_slash(RemoteIndexRoot,
+                                 llvm::sys::path::Style::windows) +
+                "lib/File.cpp")
+          .begin();
+  Ref.Location = Location;
+
+  auto Serialized = ProtobufMarshaller.toProtobuf(Ref);
+  ASSERT_TRUE(bool(Serialized));
+  // Wire path should be relative with forward slashes.
+  EXPECT_EQ(Serialized->location().file_path(), "lib/File.cpp");
+
+  auto Deserialized = ProtobufMarshaller.fromProtobuf(*Serialized);
+  ASSERT_TRUE(bool(Deserialized));
+  // Deserialized URI should be under the local root.
+  EXPECT_STREQ(Deserialized->Location.FileURI,
+               testPathURI("local/project/lib/File.cpp", Strings));
+}
+
 } // namespace
 } // namespace remote
 } // namespace clangd