Set RUSTC_WRAPPER to sccache to speed up building

CMakeLists.txt

@@ -218,6 +218,10 @@ add_test(NAME cargo_tests COMMAND cargo test --release --all-features --target-d
 add_test(NAME cargo_doc COMMAND cargo doc --release --all-features --target-dir ${CARGO_TARGET_DIR})
 add_test(NAME cargo_clippy COMMAND cargo clippy --release --all-features --target-dir ${CARGO_TARGET_DIR} -- -D warnings)
 
+if(CMAKE_RUSTC_WRAPPER)
+    list(APPEND CARGO_ENV "RUSTC_WRAPPER=set:${CMAKE_RUSTC_WRAPPER}")
+endif()
+
 set_tests_properties(cargo_tests cargo_clippy PROPERTIES
     ENVIRONMENT_MODIFICATION "${CARGO_ENV}"
 )

Cargo.toml

@@ -56,3 +56,8 @@ syn = { version = "2.0", features = ["extra-traits", "full"] }
 quote = "1.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+
+# Use a patched version of cc-rs that respects the rustc wrapper
+# This should greatly speed up CI builds!
+[patch.crates-io]
+cc = { git = "https://github.com/LeonMatthesKDAB/cc-rs.git", branch="respect-rustc-wrapper" }

cmake/CompilerCaching.cmake

@@ -1,15 +1,16 @@
 # SPDX-FileCopyrightText: 2021 Tenacity Audio Editor contributors
 # SPDX-FileContributor: Be <be.0@gmx.com>
 # SPDX-FileContributor: Emily Mabrey <emabrey@tenacityaudio.org>
+# SPDX-FileContributor: Leon Matthes <leon.matthes@kdab.com>
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #[=======================================================================[.rst:
 CompilerCaching
 ---------------
 
 Search for sccache and ccache and use them for compiler caching for C & C++.
-ccache is preferred if both are found, but the user can override this by
-explicitly setting CCACHE=OFF to use sccache when both are installed.
+sccache is preferred if both are found, but the user can override this by
+explicitly setting SCCACHE=OFF to use ccache when both are installed.
 #]=======================================================================]
 
 # ccache does not support MSVC
@@ -33,14 +34,14 @@ else()
   option(SCCACHE "Use sccache for compiler caching to speed up rebuilds." ON)
 endif()
 
-if(CCACHE)
-  message(STATUS "Using ccache for compiler caching to speed up rebuilds")
-  set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
-  set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
-elseif(SCCACHE)
+if(SCCACHE)
   message(STATUS "Using sccache for compiler caching to speed up rebuilds")
   set(CMAKE_C_COMPILER_LAUNCHER "${SCCACHE_PROGRAM}")
   set(CMAKE_CXX_COMPILER_LAUNCHER "${SCCACHE_PROGRAM}")
+  if (NOT DEFINED ENV{RUSTC_WRAPPER})
+    # Enable sccache for rustc - especially important when building cxx-qt-lib!
+    set(CMAKE_RUSTC_WRAPPER "${SCCACHE_PROGRAM}" CACHE PATH "RUSTC_WRAPPER detected by CMake")
+  endif()
 
   # Instruct MSVC to generate symbolic debug information within object files for sccache
   if(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
@@ -56,6 +57,10 @@ elseif(SCCACHE)
       string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_${CONFIG} "${CMAKE_C_FLAGS_${CONFIG}}")
     endif()
   endif()
+elseif(CCACHE)
+  message(STATUS "Using ccache for compiler caching to speed up rebuilds")
+  set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
+  set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
 else()
   if(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
     message(STATUS "No compiler caching enabled. Install sccache to speed up rebuilds.")

examples/demo_threading/CMakeLists.txt

@@ -47,6 +47,7 @@ set(CXXQT_EXPORT_DIR "${CMAKE_CURRENT_BINARY_DIR}/cxxqt")
 corrosion_set_env_vars(${CRATE}
     "CXXQT_EXPORT_DIR=${CXXQT_EXPORT_DIR}"
     "QMAKE=${QMAKE}"
+    $<$<BOOL:${CMAKE_RUSTC_WRAPPER}>:RUSTC_WRAPPER=${CMAKE_RUSTC_WRAPPER}>
 )
 
 add_library(${APP_NAME}_lib INTERFACE)

examples/qml_features/CMakeLists.txt

@@ -47,6 +47,7 @@ set(CXXQT_EXPORT_DIR "${CMAKE_CURRENT_BINARY_DIR}/cxxqt")
 corrosion_set_env_vars(${CRATE}
     "CXXQT_EXPORT_DIR=${CXXQT_EXPORT_DIR}"
     "QMAKE=${QMAKE}"
+    $<$<BOOL:${CMAKE_RUSTC_WRAPPER}>:RUSTC_WRAPPER=${CMAKE_RUSTC_WRAPPER}>
 )
 add_library(${APP_NAME}_lib INTERFACE)
 target_include_directories(${APP_NAME}_lib INTERFACE "${CXXQT_EXPORT_DIR}/${CRATE}")

examples/qml_minimal/CMakeLists.txt

@@ -64,6 +64,7 @@ set(CXXQT_EXPORT_DIR "${CMAKE_CURRENT_BINARY_DIR}/cxxqt")
 corrosion_set_env_vars(${CRATE}
     "CXXQT_EXPORT_DIR=${CXXQT_EXPORT_DIR}"
     "QMAKE=${QMAKE}"
+    $<$<BOOL:${CMAKE_RUSTC_WRAPPER}>:RUSTC_WRAPPER=${CMAKE_RUSTC_WRAPPER}>
 )
 
 # Create an INTERFACE library target to link libraries to and add include paths.

tests/basic_cxx_only/CMakeLists.txt

@@ -37,6 +37,7 @@ set(CXXQT_EXPORT_DIR "${CMAKE_CURRENT_BINARY_DIR}/cxxqt")
 corrosion_set_env_vars(${CRATE}
     "CXXQT_EXPORT_DIR=${CXXQT_EXPORT_DIR}"
     "QMAKE=${QMAKE}"
+    $<$<BOOL:${CMAKE_RUSTC_WRAPPER}>:RUSTC_WRAPPER=${CMAKE_RUSTC_WRAPPER}>
 )
 target_include_directories(${CRATE} INTERFACE "${CXXQT_EXPORT_DIR}/${CRATE}")
 target_link_libraries(${CRATE} INTERFACE

tests/basic_cxx_qt/CMakeLists.txt

@@ -37,6 +37,7 @@ set(CXXQT_EXPORT_DIR "${CMAKE_CURRENT_BINARY_DIR}/cxxqt")
 corrosion_set_env_vars(${CRATE}
     "CXXQT_EXPORT_DIR=${CXXQT_EXPORT_DIR}"
     "QMAKE=${QMAKE}"
+    $<$<BOOL:${CMAKE_RUSTC_WRAPPER}>:RUSTC_WRAPPER=${CMAKE_RUSTC_WRAPPER}>
 )
 target_include_directories(${CRATE} INTERFACE "${CXXQT_EXPORT_DIR}/${CRATE}")
 target_link_libraries(${CRATE} INTERFACE

tests/qt_types_standalone/CMakeLists.txt

@@ -37,6 +37,7 @@ set(CXXQT_EXPORT_DIR "${CMAKE_CURRENT_BINARY_DIR}/cxxqt")
 corrosion_set_env_vars(${CRATE}
     "CXXQT_EXPORT_DIR=${CXXQT_EXPORT_DIR}"
     "QMAKE=${QMAKE}"
+    $<$<BOOL:${CMAKE_RUSTC_WRAPPER}>:RUSTC_WRAPPER=${CMAKE_RUSTC_WRAPPER}>
 )
 target_include_directories(${CRATE} INTERFACE "${CXXQT_EXPORT_DIR}/${CRATE}")
 target_link_libraries(${CRATE} INTERFACE