Skip to content
Tool to import swiftc and clang index-store files into Xcode
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.
tests Clean test output before each run (#21) Jul 8, 2019
.clang-format Fix .clang-format to support v8 (#12) Jun 21, 2019
CMakeLists.txt Initial commit Jun 20, 2019 Initial commit Jun 20, 2019
LICENSE Initial commit Jun 20, 2019
NOTICE Initial commit Jun 20, 2019 Remove extra backslash in README (#18) Jun 26, 2019
index-import.cpp Fix record cloning bug (#20) Jul 8, 2019


A tool to import swiftc and clang generated indexes into Xcode.


The index-import tool makes indexes transportable. The ability to copy indexes into Xcode has a few possible uses:

  1. Using a separate build system (Bazel, Buck, CMake, SwiftPM, etc)
  2. Distributing a CI built index to developer machines
  3. Sharing an index between two or more local checkouts

The common goal is to reduce or eliminate the time Xcode spends indexing.

For Xcode to be able to use an index, the file paths contained in the index must match the paths Xcode uses for lookup. This is the main feature of index-import, rewriting the paths inside the index files. This path remapping requires knowing input and output paths.

Path remapping is done with regex substitution. index-import accepts one or more -remap flags which are formatted as <regex>=<substitution>. See the examples below. Path remapping is conceptually similar to sed s/regex/substitution/. In all cases, the substitution will either be a path within the project, or a path within DerivedData.

Index File Format

The index consists of two types of files, Unit files and Record files. Both are LLVM Bitstream, a common binary format used by LLVM/Clang/Swift. Record files contain no paths and can be simply copied. Only Unit files contain paths, so only unit files need to be rewritten. A read/write API is available in the clangIndex library. index-import uses IndexUnitReader and IndexUnitWriter.


The best information on the swiftc and clang index store comes from these two resources:


The simplest example is to consider the case of two checkouts of the same project. If one project has a built index, it can be imported into the other. To do this, two paths need to be remapped: the project directory and the build directory (DerivedData).



index-import \
    -remap "/Users/me/MyApp=/Users/me/MyApp2" \
    -remap "$build_dir1=$build_dir2" \
    "$build_dir1/Index/DataStore" \

A more complex example is importing an index from a Bazel built project. This example makes would be run as an Xcode "Run Script" build phase, which provides many environment variables, including: SRCROOT, CONFIGURATION_TEMP_DIR, ARCHS.



index-import \
    -remap "$bazel_root/$bazel_module_dir/\\1.swiftmodule=$xcode_module_dir/\$1.swiftmodule" \
    -remap "^$bazel_module_dir/.+/([^/]+).swift.o=$xcode_module_dir/\$2.o" \
    -remap "$bazel_root=$SRCROOT" \
    path/to/input/index \

Build Instructions

The build uses CMake because swift-clang uses CMake. The index-import build script is small, but depends on the larger swift-clang project. To build index-import, first build swift-clang using the Swift build instructions. Be sure to checkout a release branch of swift, not master, for example swift-5.0-branch.

Once swift has been built, index-import can be built as follows. The key step is to add the llvm bin directory from the swift build, to your PATH. This ensures CMake can find the build files it needs.

mkdir build
cd build
cmake -G Ninja -DCMAKE_BUILD_TYPE=Release ..
You can’t perform that action at this time.