fixed #14003 - made it possible to disable Boost again

.github/workflows/CI-unixish.yml

@@ -266,14 +266,42 @@ jobs:
         with:
           key: ${{ github.workflow }}-${{ github.job }}-${{ matrix.os }}
 
+      - name: Run CMake on macOS (force Boost)
+        run: |
+          # make sure we fail when Boost is requested and not available.
+          # will fail because no package configuration is available.
+          if cmake -S . -B cmake.output.boost-force-noavail -G "Unix Makefiles" -DUSE_BOOST=On; then
+            exit 1
+          else
+            exit 0
+          fi
+
       # coreutils contains "nproc"
-      - name: Install missing software on macos
+      - name: Install missing software on macOS
         run: |
           brew install coreutils boost
 
-      - name: CMake build on macOS (with Boost)
+      - name: Run CMake on macOS (force Boost)
+        run: |
+          cmake -S . -B cmake.output.boost-force -G "Unix Makefiles" -DUSE_BOOST=On
+
+      - name: Run CMake on macOS (no Boost)
+        run: |
+          # make sure Boost is not used when disabled even though it is available
+          cmake -S . -B cmake.output.boost-no -G "Unix Makefiles" -DUSE_BOOST=Off
+          if grep -q '\-DHAVE_BOOST' ./cmake.output.boost-no/compile_commands.json; then
+            exit 1
+          else
+            exit 0
+          fi
+
+      - name: Run CMake on macOS (with Boost)
         run: |
           cmake -S . -B cmake.output.boost -G "Unix Makefiles" -DBUILD_TESTS=On -DCMAKE_DISABLE_PRECOMPILE_HEADERS=On -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+          grep -q '\-DHAVE_BOOST' ./cmake.output.boost/compile_commands.json
+
+      - name: Build with CMake on macOS (with Boost)
+        run: |
           cmake --build cmake.output.boost -- -j$(nproc)
 
   build:

cmake/findDependencies.cmake

@@ -83,11 +83,12 @@ if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.30")
     cmake_policy(SET CMP0167 NEW)
 endif()
 
-# we are only using the header-only "container" component so we can unconditionally search for it
 if(USE_BOOST)
-    find_package(Boost REQUIRED)
-else()
-    find_package(Boost)
+    if(USE_BOOST STREQUAL "Auto")
+        find_package(Boost)
+    else()
+        find_package(Boost REQUIRED)
+    endif()
 endif()
 
 find_program(LIBXML2_XMLLINT_EXECUTABLE xmllint)

cmake/options.cmake

@@ -31,6 +31,7 @@ if(WARNINGS_ARE_ERRORS)
 endif()
 option(EXTERNALS_AS_SYSTEM  "Treat externals as system includes"                            OFF)
 
+# we are only using the header-only "container" Boost component so we can unconditionally search for it by default
 set(USE_MATCHCOMPILER "Auto" CACHE STRING "Usage of match compiler")
 set_property(CACHE USE_MATCHCOMPILER PROPERTY STRINGS Auto Off On Verify)
 if(USE_MATCHCOMPILER)
@@ -88,7 +89,8 @@ option(DISALLOW_THREAD_EXECUTOR "Disallow usage of ThreadExecutor for -j"
 if(DISALLOW_THREAD_EXECUTOR AND WIN32)
     message(FATAL_ERROR "Cannot disable usage of ThreadExecutor on Windows as no other executor implementation is currently available")
 endif()
-option(USE_BOOST            "Force usage of Boost"                                          OFF)
+set(USE_BOOST "Auto" CACHE STRING "Usage of Boost")
+set_property(CACHE USE_BOOST PROPERTY STRINGS Auto Off On)
 option(USE_BOOST_INT128     "Usage of Boost.Multiprecision 128-bit integer for Mathlib"     OFF)
 if (NOT USE_BOOST AND USE_BOOST_INT128)
     message(FATAL_ERROR "USE_BOOST_INT128 requires USE_BOOST to be enabled")

cmake/printInfo.cmake

@@ -87,10 +87,12 @@ if(NOT USE_BUNDLED_TINYXML2)
 endif()
 message(STATUS)
 message(STATUS "USE_BOOST =             ${USE_BOOST}")
-message(STATUS "Boost_FOUND =           ${Boost_FOUND}")
-message(STATUS "Boost_VERSION_STRING =  ${Boost_VERSION_STRING}")
-message(STATUS "Boost_INCLUDE_DIRS =    ${Boost_INCLUDE_DIRS}")
-message(STATUS "USE_BOOST_INT128 =      ${USE_BOOST_INT128}")
+if(USE_BOOST)
+    message(STATUS "Boost_FOUND =           ${Boost_FOUND}")
+    message(STATUS "Boost_VERSION_STRING =  ${Boost_VERSION_STRING}")
+    message(STATUS "Boost_INCLUDE_DIRS =    ${Boost_INCLUDE_DIRS}")
+    message(STATUS "USE_BOOST_INT128 =      ${USE_BOOST_INT128}")
+endif()
 message(STATUS)
 message(STATUS "USE_LIBCXX =            ${USE_LIBCXX}")
 message(STATUS)