COMP: Modernize Python3 module build

CMake/ITKSetPython3Vars.cmake

@@ -6,24 +6,174 @@
 # Additionally, setting Python3_EXECUTABLE can be used to set the Python version explicitly, but
 # may become less reliable with newer versions of CMake (as opposed setting FindPython3 HINTS).  Current
 # implementation gives preference to active virtualenvs.
-
 cmake_policy(SET CMP0094 NEW) # makes FindPython3 prefer activated virtualenv Python to latest version
 set(PYTHON_VERSION_MIN 3.9)
 set(PYTHON_VERSION_MAX 3.999)
-
-if(PYTHON_DEVELOPMENT_REQUIRED)
-  if(DEFINED Python3_EXECUTABLE) # if already specified
-    set(_specified_Python3_EXECUTABLE ${Python3_EXECUTABLE})
+if(DEFINED Python3_EXECUTABLE) # if already specified
+  set(_specified_Python3_EXECUTABLE ${Python3_EXECUTABLE})
+  # If a specific Python executable is provided, lock the Python version range
+  # to the exact version of that executable so FindPython3 searches that version.
+  execute_process(
+    COMMAND
+      "${_specified_Python3_EXECUTABLE}" -c
+      "import sys; print('{}.{}'.format(sys.version_info[0], sys.version_info[1]))"
+    OUTPUT_VARIABLE _specified_Python3_VERSION_MM
+    ERROR_VARIABLE _specified_Python3_VERSION_MM_ERR
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
+  if(_specified_Python3_VERSION_MM)
+    set(PYTHON_VERSION_MIN ${_specified_Python3_VERSION_MM})
+    set(PYTHON_VERSION_MAX ${_specified_Python3_VERSION_MM})
   endif()
+  unset(_specified_Python3_VERSION_MM)
+  unset(_specified_Python3_VERSION_MM_ERR)
+endif()
+
+# Tested in cmake 3.26-4.21.  Python3_FIND_ABI causes the Development COMPONENTS to not be found
+unset(Python3_FIND_ABI)
+
+if(NOT PYTHON_DEVELOPMENT_REQUIRED)
+  # if not PYTHON_DEVELOPMENT_REQUIRED, just find some version of
+  # Python (don't need to be as specific)
+  find_package(
+    Python3
+    ${PYTHON_VERSION_MIN}...${PYTHON_VERSION_MAX}
+    COMPONENTS
+      Interpreter
+  )
+  set(ITK_WRAP_PYTHON_VERSION "ITK_WRAP_PYTHON=OFF")
+else()
   # set(Python3_FIND_REGISTRY LAST) # default is FIRST. Do we need/want this?
   find_package(
     Python3
     ${PYTHON_VERSION_MIN}...${PYTHON_VERSION_MAX}
     COMPONENTS
+      Interpreter
+      # NOTE: dockcross build environments do not supply
+      #       `Development` python-dev resources
+      Development.Module
+      Development.SABIModule
+      NumPy
+  )
+  set(ITK_WRAP_PYTHON_VERSION "${Python3_VERSION}")
+
+  # start section to define package components based on LIMITED_API support and choices
+  set(_ITK_MINIMUM_SUPPORTED_LIMITED_API_VERSION 3.11)
+
+  # Force ITK_WRAP_PYTHON_VERSION if SKBUILD_SABI_COMPONENT requests it
+  string(
+    FIND
+    "${SKBUILD_SABI_COMPONENT}"
+    "SABIModule"
+    _SKBUILD_SABI_COMPONENT_REQUIRED
+  )
+  if(NOT DEFINED ITK_USE_PYTHON_LIMITED_API)
+    if(
+      (
+        _SKBUILD_SABI_COMPONENT_REQUIRED
+          GREATER
+          -1
+      )
+      OR
+        ITK_WRAP_PYTHON_VERSION
+          VERSION_GREATER_EQUAL
+          ${_ITK_MINIMUM_SUPPORTED_LIMITED_API_VERSION}
+    )
+      set(
+        ITK_USE_PYTHON_LIMITED_API
+        1
+        CACHE BOOL
+        "Configure Python's limited API for Python minor version compatibility."
+      )
+    else()
+      set(
+        ITK_USE_PYTHON_LIMITED_API
+        0
+        CACHE BOOL
+        "Configure Python's limited API for Python minor version compatibility."
+      )
+    endif()
+    mark_as_advanced(ITK_USE_PYTHON_LIMITED_API)
+  endif()
+  unset(_SKBUILD_SABI_COMPONENT_REQUIRED)
+  if(ITK_USE_PYTHON_LIMITED_API)
+    if(CMAKE_VERSION VERSION_LESS "3.26")
+      message(
+        FATAL_ERROR
+        "CMake version ${CMAKE_VERSION} is too old for Python limited API wrapping: "
+        "the FindPython Development.SABIModule component requires CMake >= 3.26. "
+        "Either upgrade CMake or disable ITK_USE_PYTHON_LIMITED_API."
+      )
+    endif()
+
+    set(
+      _python_find_components
+      Interpreter
+      Development.SABIModule
+    )
+  else()
+    set(
+      _python_find_components
       Interpreter
       Development.Module
-      ${SKBUILD_SABI_COMPONENT}
+    )
+  endif()
+  if(BUILD_TESTING)
+    # NumPy Required for testing ITK PythonTests, prefer to fail early if not installed
+    list(APPEND _python_find_components NumPy)
+  endif()
+  set(_missing_required_component FALSE)
+  find_package(
+    Python3
+    ${ITK_WRAP_PYTHON_VERSION}
+    COMPONENTS
+      ${_python_find_components}
   )
+  set(ITK_WRAP_PYTHON_VERSION "${Python3_VERSION}")
+  message(STATUS "Python3_FOUND=${Python3_FOUND}")
+  foreach(_required_component ${_python_find_components})
+    if(NOT Python3_${_required_component}_FOUND)
+      message(
+        STATUS
+        " o Python3 Missing COMPONENT: Python3_${_required_component}_FOUND: ${Python3_${_required_component}_FOUND}"
+      )
+      set(_missing_required_component TRUE)
+    else()
+      message(
+        STATUS
+        " o Python3 Found COMPONENT: Python3_${_required_component}_FOUND: ${Python3_${_required_component}_FOUND}"
+      )
+    endif()
+  endforeach()
+  unset(_required_component)
+  if(_missing_required_component)
+    message(
+      FATAL_ERROR
+      "At least 1 required Python3 COMPONENT could not be found from : ${_python_find_components}
+          in range ${PYTHON_VERSION_MIN}...${PYTHON_VERSION_MAX}:
+          Python3_EXECUTABLE=:${Python3_EXECUTABLE}:
+          ITK_WRAP_PYTHON_VERSION=:${ITK_WRAP_PYTHON_VERSION}:
+          Python3_ROOT_DIR=:${Python3_ROOT_DIR}:
+          ---
+          Python3_FOUND=${Python3_FOUND}
+          Python3_Interpreter_FOUND=${Python3_Interpreter_FOUND}
+          Python3_Compiler_FOUND=${Python3_Compiler_FOUND}
+          Python3_Development_FOUND=${Python3_Development_FOUND}
+          Python3_Development.Module_FOUND=${Python3_Development.Module_FOUND}
+          Python3_Development.SABIModule_FOUND=${Python3_Development.SABIModule_FOUND}
+          Python3_Development.Embed_FOUND=${Python3_Development.Embed_FOUND}
+          Python3_NumPy_FOUND=${Python3_NumPy_FOUND}
+    "
+    )
+  else()
+    message(STATUS " o Python3_EXECUTABLE=${Python3_EXECUTABLE}")
+    message(STATUS " o Python3_ROOT_DIR=${Python3_ROOT_DIR}")
+    message(STATUS " o ITK_WRAP_PYTHON_VERSION=${ITK_WRAP_PYTHON_VERSION}")
+  endif()
+  unset(_missing_required_component)
+  unset(_python_find_components)
+  unset(_ITK_MINIMUM_SUPPORTED_LIMITED_API_VERSION)
+  # end section to define package components based on LIMITED_API support and choices
   if(DEFINED _specified_Python3_EXECUTABLE)
     set(
       Python3_EXECUTABLE
@@ -33,35 +183,81 @@ if(PYTHON_DEVELOPMENT_REQUIRED)
       FORCE
     )
   endif()
-else() # if not PYTHON_DEVELOPMENT_REQUIRED, just find some version of Python (don't need to be as specific)
-  find_package(
-    Python3
-    ${PYTHON_VERSION_MIN}...${PYTHON_VERSION_MAX}
-    COMPONENTS
-      Interpreter
-  )
-endif()
-if(ITK_WRAP_PYTHON)
-  set(ITK_WRAP_PYTHON_VERSION "${Python3_VERSION}")
-else()
-  set(ITK_WRAP_PYTHON_VERSION "ITK_WRAP_PYTHON=OFF")
-endif()
-if(NOT Python3_EXECUTABLE AND _specified_Python3_EXECUTABLE) # workaround for cases where FindPython3 fails to set correctly
-  set(
-    Python3_EXECUTABLE
-    ${_specified_Python3_EXECUTABLE}
-    CACHE INTERNAL
-    "Path to the Python interpreter"
-    FORCE
+
+  if(NOT Python3_EXECUTABLE AND _specified_Python3_EXECUTABLE) # workaround for cases where FindPython3 fails to set correctly
+    set(
+      Python3_EXECUTABLE
+      ${_specified_Python3_EXECUTABLE}
+      CACHE INTERNAL
+      "Path to the Python interpreter"
+      FORCE
+    )
+  endif()
+
+  # If a specific Python3_EXECUTABLE is provided by the user, try to infer
+  # the corresponding Python3_ROOT_DIR for Unix/macOS/Linux so CMake's
+  # FindPython3 locates the matching installation or virtual environment.
+  # This is especially important for virtualenv/venv/conda environments.
+  if(
+    DEFINED
+      Python3_EXECUTABLE
+    AND
+      NOT
+        DEFINED
+          Python3_ROOT_DIR
+    AND
+      (
+        UNIX
+        OR
+          APPLE
+      )
+    AND
+      NOT
+        WIN32
   )
-endif()
+    # First, try sys.prefix from the provided interpreter (works for venv/conda)
+    execute_process(
+      COMMAND
+        "${Python3_EXECUTABLE}" -c "import sys; print(sys.prefix)"
+      OUTPUT_VARIABLE _py_prefix
+      ERROR_VARIABLE _py_prefix_err
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+    if(_py_prefix)
+      file(TO_CMAKE_PATH "${_py_prefix}" _py_root_hint)
+    endif()
+
+    # Fallback: parent of the interpreter's bin directory, e.g., /path/to/env
+    # from /path/to/env/bin/python3
+    if(NOT _py_root_hint)
+      get_filename_component(_py_exe_dir "${Python3_EXECUTABLE}" DIRECTORY)
+      get_filename_component(_py_root_hint "${_py_exe_dir}/.." REALPATH)
+    endif()
 
-# Add user-visible cache entry
-set(
-  Python3_ROOT_DIR
-  ${Python3_ROOT_DIR}
-  CACHE PATH
-  "Which installation or virtual environment of Python to use"
-  FORCE
-)
-mark_as_advanced(Python3_ROOT_DIR)
+    if(_py_root_hint)
+      set(
+        Python3_ROOT_DIR
+        "${_py_root_hint}"
+        CACHE PATH
+        "Which installation or virtual environment of Python to use"
+        FORCE
+      )
+      mark_as_advanced(Python3_ROOT_DIR)
+    endif()
+    unset(_py_prefix)
+    unset(_py_prefix_err)
+    unset(_py_exe_dir)
+    unset(_py_root_hint)
+  endif()
+  if(Python3_ROOT_DIR)
+    # Add user-visible cache entry if Python3_ROOT_DIR value is set
+    set(
+      Python3_ROOT_DIR
+      ${Python3_ROOT_DIR}
+      CACHE PATH
+      "Which installation or virtual environment of Python to use"
+      FORCE
+    )
+    mark_as_advanced(Python3_ROOT_DIR)
+  endif()
+endif()

CMake/ITKSetStandardCompilerFlags.cmake

@@ -446,7 +446,11 @@ macro(check_compiler_platform_flags)
       )
     endif()
 
-    check_sse2_flags(ITK_SSE2_CFLAGS_IF_AVAILABLE)
+    if(CMAKE_SIZEOF_VOID_P EQUAL 4)
+      # Setting sse2 flags only make sense on 32 bit architectures
+      # on 64bit systems, sse2 support is required, and compiler support is defaulted
+      check_sse2_flags(ITK_SSE2_CFLAGS_IF_AVAILABLE)
+    endif()
     set(
       ITK_REQUIRED_CXX_FLAGS
       "${ITK_REQUIRED_CXX_FLAGS} ${ITK_SSE2_CFLAGS_IF_AVAILABLE}"