improve detection of cases when Core can be used

CGAL_Core/include/CGAL/CORE/BigInt.h

@@ -30,7 +30,7 @@
 #include <string>
 
 
-#if !(defined(CGAL_CORE_USE_BOOST_BACKEND) && BOOST_VERSION > 107900 && defined(CGAL_USE_BOOST_MP))
+#if !(defined(CGAL_CORE_USE_BOOST_BACKEND) && BOOST_VERSION > 107900 && defined(CGAL_USE_BOOST_MP)) && !defined(CGAL_DISABLE_GMP)
 #define CGAL_CORE_USE_GMP_BACKEND 1
 #endif
 

Installation/CMakeLists.txt

@@ -115,6 +115,9 @@ option(CGAL_ENABLE_TESTING "Build the testing tree." ${BUILD_TESTING})
   endif()
 endif(CGAL_BRANCH_BUILD)
 
+#allow to force disabling boost multiprecision support
+option(CGAL_DO_NOT_USE_BOOST_MP "Disable the support of boost multiprecision library" FALSE)
+
 #message(STATUS "Packages found: ${CGAL_CONFIGURED_PACKAGES}")
 
 list(SORT CGAL_CONFIGURED_PACKAGES_NAMES)

Installation/cmake/modules/CGAL_SetupCGALDependencies.cmake

@@ -131,12 +131,6 @@ function(CGAL_setup_CGAL_flags target)
       $<$<COMPILE_LANGUAGE:CXX>:/fp:except->
       $<$<COMPILE_LANGUAGE:CXX>:/bigobj>  # Use /bigobj by default
       )
-  elseif ("${CMAKE_CXX_COMPILER_ID}" MATCHES "AppleClang")
-    if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 11.0.3)
-      message(STATUS "Apple Clang version ${CMAKE_CXX_COMPILER_VERSION} compiler detected")
-      message(STATUS "Boost MP is turned off for all Apple Clang versions below 11.0.3!")
-      target_compile_options(${target} INTERFACE "-DCGAL_DO_NOT_USE_BOOST_MP")
-    endif()
   elseif(CMAKE_CXX_COMPILER_ID MATCHES "Intel")
     message( STATUS "Using Intel Compiler. Adding -fp-model strict" )
     if(WIN32)
@@ -166,4 +160,9 @@ function(CGAL_setup_CGAL_flags target)
       target_compile_options(${target} INTERFACE "-mieee" "-mfp-rounding-mode=d" )
     endif()
   endif()
+
+  if (CGAL_DO_NOT_USE_BOOST_MP)
+    target_compile_options(${target} INTERFACE "-DCGAL_DO_NOT_USE_BOOST_MP")
+  endif()
+
 endfunction()

Installation/cmake/modules/CGAL_SetupCGAL_CoreDependencies.cmake

@@ -52,5 +52,4 @@ function(CGAL_setup_CGAL_Core_dependencies target)
   use_CGAL_GMP_support(CGAL_Core INTERFACE)
   target_compile_definitions(${target} INTERFACE CGAL_USE_CORE=1)
   target_link_libraries( CGAL_Core INTERFACE CGAL::CGAL )
-
 endfunction()

Installation/include/CGAL/Installation/internal/enable_third_party_libraries.h

@@ -35,8 +35,32 @@
 #  endif // CGAL_USE_MPFR and no <mpfr.h>
 #endif // __has_include
 
+
+// It is easier to disable this number type completely for old versions.
+// Before 1.63, I/O is broken.  Again, disabling the whole file is just the
+// easy solution.
+// MSVC had trouble with versions <= 1.69:
+// https://github.com/boostorg/multiprecision/issues/98
+//
+// Disable also on Windows 32 bits
+// because CGAL/cpp_float.h assumes _BitScanForward64 is available
+// See https://learn.microsoft.com/en-us/cpp/intrinsics/bitscanforward-bitscanforward64
+//
+// Disable also with PowerPC processors, with Boost<1.80 because of that bug:
+// https://github.com/boostorg/multiprecision/pull/421
+//
+#if !defined CGAL_DO_NOT_USE_BOOST_MP && \
+    (!defined _MSC_VER || BOOST_VERSION >= 107000) && \
+    (!defined _WIN32 || defined _WIN64) && \
+    (BOOST_VERSION >= 108000 || (!defined _ARCH_PPC && !defined _ARCH_PPC64))
+#define CGAL_USE_BOOST_MP 1
+#endif
+
+
+#if CGAL_USE_BOOST_MP
 #if ! CGAL_NO_CORE
 #  define CGAL_USE_CORE 1
 #endif
+#endif
 
 #endif // CGAL_INTERNAL_ENABLE_THIRD_PARTY_LIBRARIES_H

Installation/lib/cmake/CGAL/CGALConfig.cmake

@@ -127,12 +127,18 @@ if( CGAL_DEV_MODE OR RUNNING_CGAL_AUTO_TEST OR CGAL_TEST_SUITE )
   endif()
 endif()
 
+if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "AppleClang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 11.0.3)
+  message(STATUS "Apple Clang version ${CMAKE_CXX_COMPILER_VERSION} compiler detected")
+  message(STATUS "Boost MP is turned off for all Apple Clang versions below 11.0.3!")
+  set(CGAL_DO_NOT_USE_BOOST_MP TRUE)
+endif()
+
 foreach(comp ${CGAL_FIND_COMPONENTS})
   if(NOT comp MATCHES "Core|ImageIO|Qt6")
     message(FATAL_ERROR "The requested CGAL component ${comp} does not exist!")
   endif()
-  if(comp MATCHES "Core" AND CGAL_DISABLE_GMP)
-    message("CGAL_Core needs GMP and won't be used.")
+  if(comp MATCHES "Core" AND CGAL_DO_NOT_USE_BOOST_MP)
+    message("CGAL_Core needs Boost multiprecision support and won't be used.")
   else()
     list(APPEND CGAL_LIBRARIES CGAL_${comp})
   endif()

Number_types/include/CGAL/Number_types/internal/Exact_type_selector.h

@@ -23,7 +23,9 @@
 #include <CGAL/MP_Float.h>
 #include <CGAL/Quotient.h>
 
+#ifdef CGAL_USE_BOOST_MP
 #include <CGAL/cpp_float.h>
+#endif
 
 #ifdef CGAL_USE_GMP
 #  include <CGAL/Gmpz.h>

Number_types/include/CGAL/boost_mp_type.h

@@ -15,24 +15,9 @@
 #include <CGAL/config.h>
 #include <CGAL/number_utils.h>
 
-// It is easier to disable this number type completely for old versions.
-// Before 1.63, I/O is broken.  Again, disabling the whole file is just the
-// easy solution.
-// MSVC had trouble with versions <= 1.69:
-// https://github.com/boostorg/multiprecision/issues/98
-//
-// Disable also on Windows 32 bits
-// because CGAL/cpp_float.h assumes _BitScanForward64 is available
-// See https://learn.microsoft.com/en-us/cpp/intrinsics/bitscanforward-bitscanforward64
-//
-// Disable also with PowerPC processors, with Boost<1.80 because of that bug:
-// https://github.com/boostorg/multiprecision/pull/421
-//
-#if !defined CGAL_DO_NOT_USE_BOOST_MP && \
-    (!defined _MSC_VER || BOOST_VERSION >= 107000) && \
-    (!defined _WIN32 || defined _WIN64) && \
-    (BOOST_VERSION >= 108000 || (!defined _ARCH_PPC && !defined _ARCH_PPC64))
-#define CGAL_USE_BOOST_MP 1
+// CGAL_USE_BOOST_MP is defined in
+// CGAL/Installation/internal/enable_third_party_libraries.h
+#if CGAL_USE_BOOST_MP
 
 #include <CGAL/Quotient.h>
 #include <CGAL/functional.h> // *ary_function