Allow ccache to reuse results across build directories (#1087)

Author: eramongodb

.evergreen/abi-stability-setup.sh

@@ -56,10 +56,14 @@ else
 fi
 
 # Use ccache if available.
-if command -V ccache; then
-  export CMAKE_C_COMPILER_LAUNCHER CMAKE_CXX_COMPILER_LAUNCHER
-  CMAKE_C_COMPILER_LAUNCHER="ccache"
-  CMAKE_CXX_COMPILER_LAUNCHER="ccache"
+if command -V ccache 2>/dev/null; then
+  export CMAKE_C_COMPILER_LAUNCHER=ccache
+  export CMAKE_CXX_COMPILER_LAUNCHER=ccache
+
+  # Allow reuse of ccache compilation results between different build directories.
+  export CCACHE_BASEDIR CCACHE_NOHASHDIR
+  CCACHE_BASEDIR="$(pwd)/mongo-cxx-driver"
+  CCACHE_NOHASHDIR=1
 fi
 
 # Install prefix to use for ABI compatibility scripts.

.evergreen/compile.sh

@@ -67,10 +67,18 @@ CMAKE_BUILD_PARALLEL_LEVEL="$(nproc)"
 export CMAKE_BUILD_PARALLEL_LEVEL
 
 # Use ccache if available.
-if command -v ccache >/dev/null; then
-  echo "Enabling ccache as CMake compiler launcher"
-  export CMAKE_C_COMPILER_LAUNCHER=ccache
+if command -V ccache 2>/dev/null; then
   export CMAKE_CXX_COMPILER_LAUNCHER=ccache
+
+
+  # Allow reuse of ccache compilation results between different build directories.
+  export CCACHE_BASEDIR CCACHE_NOHASHDIR
+  CCACHE_BASEDIR="$(pwd)"
+  CCACHE_NOHASHDIR=1
+  # Allow reuse of ccache compilation results between different build directories.
+  export CCACHE_BASEDIR CCACHE_NOHASHDIR
+  CCACHE_BASEDIR="$(pwd)"
+  CCACHE_NOHASHDIR=1
 fi
 
 cmake_build_opts=()

.evergreen/install_c_driver.sh

@@ -83,7 +83,6 @@ if [[ "${OSTYPE}" == darwin* ]]; then
   }
 fi
 
-
 # Default CMake generator to use if not already provided.
 declare CMAKE_GENERATOR CMAKE_GENERATOR_PLATFORM
 if [[ "${OSTYPE:?}" == "cygwin" ]]; then
@@ -131,6 +130,17 @@ else
   configure_flags+=("-DENABLE_EXTRA_ALIGNMENT=OFF")
 fi
 
+# Use ccache if available.
+if command -V ccache 2>/dev/null; then
+  export CMAKE_C_COMPILER_LAUNCHER=ccache
+  export CMAKE_CXX_COMPILER_LAUNCHER=ccache
+
+  # Allow reuse of ccache compilation results between different build directories.
+  export CCACHE_BASEDIR CCACHE_NOHASHDIR
+  CCACHE_BASEDIR="${mongoc_idir}"
+  CCACHE_NOHASHDIR=1
+fi
+
 # Install libmongoc.
 {
   echo "Installing C Driver into ${mongoc_dir}..." 1>&2

.mci.yml

@@ -962,11 +962,21 @@ tasks:
             rsync -aq --exclude='examples/add_subdirectory' $(readlink -f ../..) .
             [ -d build ] || mkdir build
             . ./mongo-c-driver/.evergreen/scripts/find-cmake-latest.sh
-            export CMAKE
-            CMAKE="$(find_cmake_latest)"
-            command -v "$CMAKE"
-            $CMAKE -S . -B build -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF
-            $CMAKE --build build
+            export cmake_binary
+            cmake_binary="$(find_cmake_latest)"
+            # Use ccache if available.
+            if command -V ccache 2>/dev/null; then
+              export CMAKE_C_COMPILER_LAUNCHER=ccache
+              export CMAKE_CXX_COMPILER_LAUNCHER=ccache
+
+              # Allow reuse of ccache compilation results between different build directories.
+              export CCACHE_BASEDIR CCACHE_NOHASHDIR
+              CCACHE_BASEDIR="$(pwd)"
+              CCACHE_NOHASHDIR=1
+            fi
+            command -v "$cmake_binary"
+            "$cmake_binary" -S . -B build -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF
+            "$cmake_binary" --build build
             ./build/hello_mongocxx
 
     - name: debian-package-build