Modifications to build C++ with Visual Studio 2026 and the v145 toolset. (#9359)

* Modifications to build C++ with Visual Studio 2026 and the v145 toolset.

* Fixes linker settings for rocksdb for Debug and Release builds

* module is a C++ 20 keyword. Explicitly stating namespace allows cpp20 projects to build against the library

* Fixes crash when initializing an object with the initialize function when some of the attributes are empty, {}, or omitted, std::nullopt

* cleanup for vs2026 v145 toolset per @aothms review

* Fixes bug, IfcCurveSegment.setStartLength was setSegmentLength in alignment_helper.cpp

* Bumps boost to 1.92

cmake/CMakeLists.txt

@@ -178,26 +178,31 @@ if((BUILD_CONVERT OR BUILD_GEOMSERVER OR BUILD_IFCPYTHON) AND(NOT BUILD_IFCGEOM)
     set(BUILD_IFCGEOM ON)
 endif()
 
-find_program(CCACHE_FOUND ccache)
-if(CCACHE_FOUND)
-    message(STATUS "`ccache` is found, using it as a compiler launcher.")
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_FOUND}")
-    if(MSVC)
-        # By default Visual Studio generators will use /Zi which is not compatible
-        # with ccache, so tell Visual Studio to use /Z7 instead.
-        set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<$<CONFIG:Debug,RelWithDebInfo>:Embedded>")
-        # Not needed for Ninja.
-        if(CMAKE_GENERATOR MATCHES "Visual Studio")
-            file(COPY_FILE
-                ${CCACHE_FOUND} ${CMAKE_BINARY_DIR}/cl.exe
-                ONLY_IF_DIFFERENT)
-            set(CMAKE_VS_GLOBALS
-                "CLToolExe=cl.exe"
-                "CLToolPath=${CMAKE_BINARY_DIR}"
-                "UseMultiToolTask=true"
-            )
+option(USE_CCACHE "Use ccache as a compiler launcher if it is found" OFF)
+if(USE_CCACHE)
+    find_program(CCACHE_FOUND ccache)
+    if(CCACHE_FOUND)
+        message(STATUS "`ccache` is found, using it as a compiler launcher.")
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_FOUND}")
+        if(MSVC)
+            # By default Visual Studio generators will use /Zi which is not compatible
+            # with ccache, so tell Visual Studio to use /Z7 instead.
+            set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<$<CONFIG:Debug,RelWithDebInfo>:Embedded>")
+            # Not needed for Ninja.
+            if(CMAKE_GENERATOR MATCHES "Visual Studio")
+                file(COPY_FILE
+                    ${CCACHE_FOUND} ${CMAKE_BINARY_DIR}/cl.exe
+                    ONLY_IF_DIFFERENT)
+                set(CMAKE_VS_GLOBALS
+                    "CLToolExe=cl.exe"
+                    "CLToolPath=${CMAKE_BINARY_DIR}"
+                    "UseMultiToolTask=true"
+                )
+            endif()
         endif()
     endif()
+else()
+    message(STATUS "ccache usage disabled via USE_CCACHE=OFF")
 endif()
 
 if(MSVC AND MSVC_PARALLEL_BUILD)
@@ -311,12 +316,25 @@ if (WITH_ROCKSDB)
     set(SWIG_DEFINES ${SWIG_DEFINES} -DIFOPSH_WITH_ROCKSDB)
     # See https://github.com/facebook/rocksdb/issues/981.
     if(TARGET RocksDB::rocksdb)
-        target_link_libraries(IFCOPENSHELL_RocksDB INTERFACE RocksDB::rocksdb)
+        set(IFCOPENSHELL_ROCKSDB_IMPORTED_TARGET RocksDB::rocksdb)
     elseif(TARGET RocksDB::rocksdb-shared)
-        target_link_libraries(IFCOPENSHELL_RocksDB INTERFACE RocksDB::rocksdb-shared)
+        set(IFCOPENSHELL_ROCKSDB_IMPORTED_TARGET RocksDB::rocksdb-shared)
     else()
         message(FATAL_ERROR "RocksDB found but neither RocksDB::rocksdb nor RocksDB::rocksdb-shared target exists")
     endif()
+    # Our win/build-deps.cmd builds RocksDB separately per Debug/Release config into the
+    # same install prefix, so the imported target only ever has DEBUG and RELEASE listed in
+    # IMPORTED_CONFIGURATIONS. On a multi-config generator (Visual Studio), CMake maps any
+    # unmatched build config to the *first* entry of that list, which happens to be DEBUG
+    # (RocksDBTargets-debug.cmake sorts before RocksDBTargets-release.cmake). Without an
+    # explicit mapping, RelWithDebInfo and MinSizeRel builds would end up linking the
+    # /MDd-flavored rocksdb_d.lib into an /MD (NDEBUG) binary, causing a CRT/runtime-library
+    # mismatch that depends on nothing but that alphabetical ordering.
+    set_target_properties(${IFCOPENSHELL_ROCKSDB_IMPORTED_TARGET} PROPERTIES
+        MAP_IMPORTED_CONFIG_RELWITHDEBINFO RELEASE
+        MAP_IMPORTED_CONFIG_MINSIZEREL RELEASE
+    )
+    target_link_libraries(IFCOPENSHELL_RocksDB INTERFACE ${IFCOPENSHELL_ROCKSDB_IMPORTED_TARGET})
 
     if (WITH_ZSTD)
         # @todo do we actually need the zstd include dir or rather just pass

src/ifcparse/alignment_helper.cpp

@@ -536,7 +536,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         auto curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -549,7 +549,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         auto curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, length * start_radius / std::fabs(start_radius)));
         curve_segment.setParentCurve(parent_curve);
 
@@ -570,7 +570,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         auto curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, offset));
+        curve_segment.setSegmentStart(create_length(file, offset));
         curve_segment.setSegmentLength(create_length(file, length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -606,7 +606,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -628,7 +628,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -659,7 +659,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, offset));
+        curve_segment.setSegmentStart(create_length(file, offset));
         curve_segment.setSegmentLength(create_length(file, length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -692,7 +692,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment1 = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment1.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment1.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment1.setSegmentLength(create_length(file, 0.0));
+        curve_segment1.setSegmentStart(create_length(file, 0.0));
         curve_segment1.setSegmentLength(create_length(file, length / 2));
         curve_segment1.setParentCurve(parent_curve1);
 
@@ -724,7 +724,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment2 = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment2.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment2.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment2.setSegmentLength(create_length(file, length / 2));
+        curve_segment2.setSegmentStart(create_length(file, length / 2));
         curve_segment2.setSegmentLength(create_length(file, length / 2));
         curve_segment2.setParentCurve(parent_curve2);
 
@@ -756,7 +756,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_point.Coordinates()[0], start_point.Coordinates()[1], cos(start_direction), sin(start_direction)));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -795,7 +795,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         auto curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_distance_along, start_height, dx, dy));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, segment_curve_length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -822,7 +822,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         auto curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_distance_along, start_height, dx, dy));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, segment_curve_length));
         curve_segment.setParentCurve(parent_curve);
 
@@ -848,7 +848,7 @@ std::pair<Ifc4x3_add2::IfcCurveSegment, Ifc4x3_add2::IfcCurveSegment> mapAlignme
         Ifc4x3_add2::IfcCurveSegment curve_segment = file.create<Ifc4x3_add2::IfcCurveSegment>();
         curve_segment.setTransition(Ifc4x3_add2::IfcTransitionCode::IfcTransitionCode_CONTSAMEGRADIENT);
         curve_segment.setPlacement(file.addPlacement2d(start_distance_along, start_height, 1.0, 0.));
-        curve_segment.setSegmentLength(create_length(file, 0.0));
+        curve_segment.setSegmentStart(create_length(file, 0.0));
         curve_segment.setSegmentLength(create_length(file, segment_curve_length));
         curve_segment.setParentCurve(parent_curve);
 

src/ifcparse/parse.cpp

@@ -1651,27 +1651,42 @@ express::base::set_attribute_value(size_t i, const T& t) {
         apply_individual_instance_visitor(current_attribute, (int)i).apply(visitor);
     }
 
-    data()->set_attribute_value(i, t);
-    auto new_attribute = get_attribute_value(i);
-
-    // Register inverse indices in file
-    if constexpr (std::is_same_v<T, express::base> || std::is_same_v<T, std::vector<express::base>> || std::is_same_v<T, std::vector<std::vector<express::base>>>) {
-        register_inverse_visitor visitor(*file(), *this);
-        apply_individual_instance_visitor(new_attribute, (int)i).apply(visitor);
+    // A null/empty single instance attribute (e.g. an omitted optional like
+    // OwnerHistory, ObjectPlacement or Representation) must not be persisted
+    // as a "set" attribute: doing so leaves isNull() false for it afterwards,
+    // so generated getters proceed to as<T>() and dereference a null instance.
+    bool should_set = true;
+    if constexpr (std::is_same_v<T, express::base>) {
+        should_set = static_cast<bool>(t);
     }
 
-    // Register new attribute guid in guid map
-    if (i == 0 && (file()->ifcroot_type() != nullptr) && this->declaration().is(*file()->ifcroot_type())) {
-        try {
-            auto guid = (std::string) new_attribute;
-            auto it = file()->internal_guid_map().find(guid);
-            if (it != file()->internal_guid_map().end()) {
-                file()->logger().warning("Duplicate guid " + guid);
-            }
-            file()->internal_guid_map().insert({guid, *this});
-        } catch (ifcopenshell::exception& e) {
-            file()->logger().error(e);
+    if (should_set) {
+        data()->set_attribute_value(i, t);
+        auto new_attribute = get_attribute_value(i);
+
+        // Register inverse indices in file
+        if constexpr (std::is_same_v<T, express::base> || std::is_same_v<T, std::vector<express::base>> || std::is_same_v<T, std::vector<std::vector<express::base>>>) {
+            register_inverse_visitor visitor(*file(), *this);
+            apply_individual_instance_visitor(new_attribute, (int)i).apply(visitor);
         }
+
+        // Register new attribute guid in guid map
+        if (i == 0 && (file()->ifcroot_type() != nullptr) && this->declaration().is(*file()->ifcroot_type())) {
+            try {
+                auto guid = (std::string) new_attribute;
+                auto it = file()->internal_guid_map().find(guid);
+                if (it != file()->internal_guid_map().end()) {
+                    file()->logger().warning("Duplicate guid " + guid);
+                }
+                file()->internal_guid_map().insert({guid, *this});
+            } catch (ifcopenshell::exception& e) {
+                file()->logger().error(e);
+            }
+        }
+    } else if (!current_attribute.isNull()) {
+        // The attribute previously held a value, so record the clearing
+        // explicitly as blank instead of silently leaving the old value in place.
+        data()->set_attribute_value(i, blank{});
     }
 }
 

src/plugin/plugin.h

@@ -96,7 +96,7 @@ public:
 
 	std::vector<std::filesystem::path> discover(const std::string& basename_prefix) const;
 	std::vector<std::filesystem::path> discover_exact(const std::string& basename) const;
-	module load(const std::filesystem::path& path) const;
+	ifcopenshell::plugin::module load(const std::filesystem::path& path) const;
 
 private:
 	std::vector<std::filesystem::path> search_paths_;

win/build-deps.cmd

@@ -123,7 +123,7 @@ if "%CMAKE_VERSION%" LSS "cmake version 3.11.4" (
 )
 
 :: NOTE Boost < 1.64 doesn't work without tricks if the user has only VS 2017 installed and no earlier versions.
-set BOOST_VERSION=1.86.0
+set BOOST_VERSION=1.92.0
 :: Version string with underscores instead of dots.
 set BOOST_VER=%BOOST_VERSION:.=_%
 
@@ -464,6 +464,10 @@ cd "%DEPENDENCY_DIR%"
 :: so disable it from the build altogether as we have no use for it
 findstr #add_subdirectory(COLLADAValidator) CMakeLists.txt>NUL
 IF NOT %ERRORLEVEL%==0 git apply --reject --whitespace=fix "%~dp0patches\OpenCOLLADA_CMakeLists.txt.patch" --ignore-whitespace
+:: std::tr1::unordered_map was a legacy MSVC compatibility shim kept around through VS2022's STL, but newer
+:: toolsets (e.g. VS2026/v145) no longer provide it, breaking the build with error C2039: 'tr1' is not a member of 'std'.
+findstr /C:"typedef std::unordered_map<MarkId, FilePosType > MarkIdToFilePos;" common\libBuffer\include\CommonFWriteBufferFlusher.h>NUL
+IF NOT %ERRORLEVEL%==0 git apply --reject --whitespace=fix "%~dp0patches\OpenCOLLADA_CommonFWriteBufferFlusher_tr1.patch" --ignore-whitespace
 :: NOTE OpenCOLLADA has been observed to have problems with switching between debug and release builds so
 :: uncomment to following line in order to delete the CMakeCache.txt always if experiencing problems.
 REM IF EXIST "%DEPENDENCY_DIR%\%BUILD_DIR%\CMakeCache.txt". del "%DEPENDENCY_DIR%\%BUILD_DIR%\CMakeCache.txt"
@@ -747,7 +751,12 @@ set QT6_MSVC_YEAR=%VS_VER%
 IF /I "%VS_TOOLSET%"=="v141" set QT6_MSVC_YEAR=2017
 IF /I "%VS_TOOLSET%"=="v142" set QT6_MSVC_YEAR=2019
 IF /I "%VS_TOOLSET%"=="v143" set QT6_MSVC_YEAR=2022
-IF /I "%VS_TOOLSET%"=="v145" set QT6_MSVC_YEAR=2026
+:: Qt has not published prebuilt msvc2026 binaries yet (aqt only lists win64_msvc2022_64 as of
+:: Qt 6.7-6.10). The v14x MSVC toolsets share a stable ABI/CRT, so fall back to the msvc2022
+:: binaries until Qt ships msvc2026 ones. Revisit once `aqt list-qt windows desktop --arch <ver>`
+:: shows a msvc2026 entry.
+IF /I "%VS_TOOLSET%"=="v145" set QT6_MSVC_YEAR=2022
+IF "%VS_VER%"=="2026" set QT6_MSVC_YEAR=2022
 
 set QT6_ARCH=
 set QT6_INSTALL_SUFFIX=

win/patches/OpenCOLLADA_CommonFWriteBufferFlusher_tr1.patch

@@ -0,0 +1,13 @@
+diff --git a/common/libBuffer/include/CommonFWriteBufferFlusher.h b/common/libBuffer/include/CommonFWriteBufferFlusher.h
+index c7af45b2..62b0f991 100644
+--- a/common/libBuffer/include/CommonFWriteBufferFlusher.h
++++ b/common/libBuffer/include/CommonFWriteBufferFlusher.h
+@@ -58,7 +58,7 @@ namespace Common
+ #else
+ 		typedef __int64 FilePosType;
+ #endif
+-	typedef std::tr1::unordered_map<MarkId, FilePosType > MarkIdToFilePos;
++	typedef std::unordered_map<MarkId, FilePosType > MarkIdToFilePos;
+ 
+ 	public:
+ 		static const size_t DEFAUL_BUFFER_SIZE = 64*1024;

win/run-cmake.bat

@@ -20,10 +20,14 @@
 :: Example usage:
 ::   run-cmake.bat vs2022-x64
 ::   run-cmake.bat vs2022-x64 -DGLTF_SUPPORT=ON
+::   run-cmake.bat vs2022-x64 -DUSE_CCACHE=OFF
 ::
 :: Used environment variables:
 :: - `ADD_COMMIT_SHA` - if defined then `ADD_COMMIT_SHA` and `VERSION_OVERRIDE` cmake args will be set to `ON`.
 :: - `USE_NINJA` - if defined then the Ninja generator will be used instead of the Visual Studio.
+::
+:: -DUSE_CCACHE=OFF (also accepts 0/FALSE/NO/N) disables ccache: the bundled ccache
+:: install dir is kept out of CMAKE_PREFIX_PATH, and CMakeLists.txt skips detecting it.
 
 
 @if not defined ECHO_ON ( echo off )
@@ -81,6 +85,27 @@ if not (%1)==() (
     call set ARGUMENTS=%%ARGUMENTS:%1=%%
 )
 
+:: Honor -DUSE_CCACHE=OFF (also accepts 0/FALSE/NO/N, case-insensitive) by keeping
+:: the bundled ccache out of CMAKE_PREFIX_PATH so it can't be auto-detected below.
+set USE_CCACHE_VALUE=
+for %%A in (%*) do (
+    set "ARG=%%~A"
+    if not "!ARG:-DUSE_CCACHE=!"=="!ARG!" (
+        for /f "tokens=2 delims==" %%V in ("!ARG!") do set "USE_CCACHE_VALUE=%%V"
+    )
+)
+if defined USE_CCACHE_VALUE (
+    if /I "!USE_CCACHE_VALUE!"=="OFF"   set DISABLE_CCACHE=1
+    if /I "!USE_CCACHE_VALUE!"=="0"     set DISABLE_CCACHE=1
+    if /I "!USE_CCACHE_VALUE!"=="FALSE" set DISABLE_CCACHE=1
+    if /I "!USE_CCACHE_VALUE!"=="NO"    set DISABLE_CCACHE=1
+    if /I "!USE_CCACHE_VALUE!"=="N"     set DISABLE_CCACHE=1
+)
+if defined DISABLE_CCACHE (
+    echo USE_CCACHE=%USE_CCACHE_VALUE% passed, disabling ccache.
+    set "CCACHE_INSTALL_DIR="
+)
+
 pushd ..
 set CMAKE_INSTALL_PREFIX=%CD%\_installed-%GEN_SHORTHAND%
 popd