Implement features required by Xcode

.github/workflows/integration-tests.yml

@@ -894,3 +894,53 @@ jobs:
           cargo clean && cargo build
       - name: lv10-stats-use
         run: ${SCCACHE_PATH} --show-stats
+
+  xcode:
+    runs-on: macos-latest
+    env:
+      SCCACHE_PATH: target/debug/sccache
+    steps:
+      - name: Clone repository
+        uses: actions/checkout@v4
+
+      - name: Install rust
+        uses: ./.github/actions/rust-toolchain
+        with:
+          toolchain: "stable"
+
+      - name: Build sccache
+        run: |
+          cargo build
+
+      - name: Create wrapper script
+        working-directory: tests/xcode
+        run: |
+          echo '#!/bin/sh' > wrapper.sh
+          echo "$GITHUB_WORKSPACE/${SCCACHE_PATH} $(xcrun -f cc) \$@" >> wrapper.sh
+          chmod +x wrapper.sh
+          echo "Wrapper script:"
+          cat wrapper.sh
+
+      - name: Start server
+        run: ${SCCACHE_PATH} --start-server
+
+      - name: Test compile xcode
+        working-directory: tests/xcode
+        run: |
+          xcodebuild -version
+          xcodebuild -xcconfig sccache.xcconfig
+
+      - name: Output
+        run: |
+          ${SCCACHE_PATH} --show-stats
+
+      - name: Test compile xcode cached
+        working-directory: tests/xcode
+        run: |
+          xcodebuild clean
+          xcodebuild -xcconfig sccache.xcconfig
+
+      - name: Output
+        run: |
+          ${SCCACHE_PATH} --show-stats
+          ${SCCACHE_PATH} --show-stats | grep -e "Cache hits\s*[1-9]"

docs/Xcode.md

@@ -0,0 +1,116 @@
+# Using `sccache` with Xcode
+
+It is possible to use `sccache` with Xcode with some setup.
+
+### Running the daemon
+Before building, you need to run the daemon outside of Xcode. This needs to be done because if `sccache` invocation happens to implicitly start the server daemon, the Xcode build will hang on the `sccache` invocation, waiting for the process to idle timeout.
+
+You can do this in another terminal windows by calling
+```sh
+SCCACHE_LOG=info SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache
+```
+
+Or by setting it up in a `launchd` configuration, perhaps as `~/Library/LaunchAgents/sccache.plist` (note the paths in the plist):
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+  <dict>
+    <key>Label</key>
+    <string>sccache.server</string>
+    <key>ProgramArguments</key>
+    <array>
+      <string>/path/to/sccache</string>
+    </array>
+    <key>EnvironmentVariables</key>
+    <dict>
+        <key>SCCACHE_START_SERVER</key>
+        <string>1</string>
+        <key>SCCACHE_NO_DAEMON</key>
+        <string>1</string>
+        <key>SCCACHE_IDLE_TIMEOUT</key>
+        <string>0</string>
+        <key>SCCACHE_LOG</key>
+        <string>info</string>
+    </dict>
+
+    <key>StandardOutPath</key>
+    <string>/tmp/sccache.log</string>
+    <key>StandardErrorPath</key>
+    <string>/tmp/sccache.log</string>
+
+  </dict>
+</plist>
+```
+
+### Setting it up for `xcodebuild`
+When you override the `CC` variable for `xcodebuild`, it seems to always escape the spaces, so its not enough to just set it, but we need a wrapper script, something like
+
+```sh
+echo "#\!/bin/sh\nsccache $(xcrun -f cc) \$@" > wrapper.sh
+chmod +x wrapper.sh
+```
+(YMMV if you need to select another sdk or toolchain for the xcrun)
+
+Then you can invoke `xcodebuild` like so
+```sh
+xcodebuild CC="$(pwd)/wrapper.sh"
+           CLANG_ENABLE_MODULES=NO
+           COMPILER_INDEX_STORE_ENABLE=NO
+```
+Where the additional arguments are for disabling some features that `sccache` can't cache currently.
+
+These build settings can also be put in a xcconfig file, like `sccache.xcconfig`
+```
+CC=$(SRCROOT)/wrapper.sh
+CLANG_ENABLE_MODULES=NO
+COMPILER_INDEX_STORE_ENABLE=NO
+```
+Which can then be invoked with
+```sh
+xcodebuild -xcconfig sccache.xcconfig
+```
+
+
+### Setting it up for `cmake` Xcode generator
+While `cmake` has the convenient `CMAKE_<LANG>_COMPILER_LAUNCHER` for prepending tools like `sccache`, it is not supported for the Xcode generator.
+
+It can be then integrated with having a template file for the wrapper script, `launcher.sh.in`:
+```sh
+#!/bin/sh
+exec "${CCACHE_EXE}" "${LAUNCHER_COMPILER}" "$@"
+```
+
+And then configuring it something like
+```cmake
+
+# This bit before the first `project()`, as the COMPILER_LAUNCHER variables are read in then
+if(DEFINED CCACHE)
+	find_program(CCACHE_EXE ${CCACHE} REQUIRED)
+	if(NOT CMAKE_GENERATOR STREQUAL "Xcode")
+		# Support for other generators should work with these
+		set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_EXE}")
+		set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_EXE}")
+	endif()
+endif()
+
+# .. your project stuff ..
+
+# This bit needs to be after the first `project()` call, to have valid `CMAKE_C_COMPILER` variable.
+# Alternatively in a file included with CMAKE_PROJECT_INCLUDE
+if(DEFINED CCACHE)
+	if(CMAKE_GENERATOR STREQUAL "Xcode")
+		set(LAUNCHER_COMPILER ${CMAKE_C_COMPILER})
+		configure_file(${CMAKE_CURRENT_LIST_DIR}/launcher.sh.in launcher-cc.sh)
+		execute_process(COMMAND chmod a+rx
+		"${CMAKE_CURRENT_BINARY_DIR}/launcher-cc.sh")
+		set(CMAKE_XCODE_ATTRIBUTE_CC "${CMAKE_CURRENT_BINARY_DIR}/launcher-cc.sh")
+		set(CMAKE_XCODE_ATTRIBUTE_CLANG_ENABLE_MODULES "NO")
+		set(CMAKE_XCODE_ATTRIBUTE_COMPILER_INDEX_STORE_ENABLE "NO")
+	endif()
+endif()
+```
+Then configuring with `-DCCACHE=sccache` should work on all generators.
+
+
+