Due to the introduction of precompiled headers, ccache builds require setting 'ccache -set-config sloppiness=pch_defines,time_macros'

.ci/ogc/build.sh

@@ -13,6 +13,9 @@ ccache -M 2.0G
 # export CCACHE_LOGFILE=/tmp/cache.debug
 ccache -z
 
+# To make ccache work properly with precompiled headers
+ccache --set-config sloppiness=pch_defines,time_macros
+
 cmake -GNinja \
  -DUSE_CCACHE=ON \
  -DWITH_QUICK=OFF \

.docker/docker-qgis-build.sh

@@ -18,6 +18,9 @@ ccache -M 2.0G
 # export CCACHE_LOGFILE=/tmp/cache.debug
 ccache -z
 
+# To make ccache work properly with precompiled headers
+ccache --set-config sloppiness=pch_defines,time_macros
+
 ##############################
 # Variables for output styling
 ##############################

.github/workflows/macos-build.yml

@@ -108,6 +108,8 @@ jobs:
           mkdir -p ${CCACHE_DIR}
           brew install ccache
           ccache --set-config=max_size=2.0G
+          # To make ccache work properly with precompiled headers
+          ccache --set-config sloppiness=pch_defines,time_macros
           ccache -s
 
       - name: Run cmake

.github/workflows/windows-qt6.yml

@@ -53,6 +53,12 @@ jobs:
           key: build-ccache-win64-qt6-${{ github.event.pull_request.base.ref || github.ref_name }}
           save: ${{ github.event_name == 'push' }}
 
+      - name: 🛍️ Tune ccache configuration
+        shell: bash
+        run: |
+          # To make ccache work properly with precompiled headers
+          ccache --set-config sloppiness=pch_defines,time_macros
+
       - name: 🌱 Install dependencies and generate project files
         shell: bash
         run: |

CMakeLists.txt

@@ -125,9 +125,28 @@ option(USE_CCACHE "Use ccache" ON)
 if (USE_CCACHE)
   find_program(CCACHE_FOUND ccache)
   if(CCACHE_FOUND)
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
     message(STATUS "ccache found")
+    execute_process(COMMAND ccache --help OUTPUT_STRIP_TRAILING_WHITESPACE OUTPUT_VARIABLE CCACHE_HELP)
+    execute_process(COMMAND ccache --get-config sloppiness OUTPUT_STRIP_TRAILING_WHITESPACE OUTPUT_VARIABLE CCACHE_SLOPPINESS)
+    string(FIND "${CCACHE_SLOPPINESS}" "pch_defines" fpch_defines_found_index)
+    string(FIND "${CCACHE_SLOPPINESS}" "time_macros" time_macros_found_index)
+    # Detect if we have ccache >= 4.8 which accepts passing configuration settings when invoking the compiler
+    string(FIND "${CCACHE_HELP}" "ccache [KEY=VALUE ...] compiler" ccache_key_value_found_index)
+    if (ccache_key_value_found_index EQUAL -1 )
+      if (fpch_defines_found_index EQUAL -1 OR time_macros_found_index EQUAL -1)
+          message(FATAL_ERROR "The use of precompiled headers only work if the ccache 'sloppiness' settings contains 'pch_defines' and 'time_macros'. Consider running 'ccache --set-config sloppiness=pch_defines,time_macros' to define them")
+      endif()
+      set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+      set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+    else()
+      if (fpch_defines_found_index EQUAL -1 OR time_macros_found_index EQUAL -1)
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "ccache sloppiness=pch_defines,time_macros")
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK "ccache sloppiness=pch_defines,time_macros")
+      else()
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+      endif()
+    endif()
   endif(CCACHE_FOUND)
 endif(USE_CCACHE)
 

ms-windows/mingw/build.sh

@@ -67,6 +67,9 @@ fi
 installroot="$BUILDDIR/dist"
 installprefix="$installroot/usr/$arch-w64-mingw32/sys-root/mingw"
 
+# To make ccache work properly with precompiled headers
+ccache --set-config sloppiness=pch_defines,time_macros
+
 # Cleanup
 rm -rf "$installroot"