build: improve python check for Windows

[compnerd]

Summary

If we have a new enough CMake, use find_package(Python3). This version is able to check both 32-bit and 64-bit versions and will setup everything properly without the user needing to specify PYTHON_HOME. This enables building lldb's python bindings on Windows under Azure's CI again.

[JDevlieghere]

I proposed this in https://reviews.llvm.org/D64881 and the consensus was that we didn't want to do this.

Also I don't think this should be a Windows-only thing.

[compnerd]

The reason for bringing this back up as a Windows specific thing is that currently, there is no good way to build LLDB with python support without having to specify additional details on *just* windows because the windows path is doing something special. This is trying to bring the windows path to parity with the Linux path.

[labath]

Yeah, I'd still like to avoid having multiple paths for configuring python, as one of them is bound to end up broken sooner or later. However, given that there's already talk about bumping the minimum cmake version, maybe we could do an lldb-specific bump first?

Though I am generally against aggressive version bumps, this python+windows situation is sufficiently messy that I think the bump may be worth it. Given that this code is python3 specific and other platforms still support python2, maybe we can make this bump windows-specific at first, and then extend it to other platforms once we officially stop supporting python2 ?

[+ other windows stakeholders: @amccarth, @ted, @aleksandr.urakov ]

lldb/cmake/modules/LLDBConfig.cmake

225

What if I use a single-config generator and build a release configuration. Is the "development" thingy still required?

[compnerd]

Yeah, doing an incremental rollout makes sense.

lldb/cmake/modules/LLDBConfig.cmake

225

Yes, it is - the component is the headers for building.

[amccarth]

In D69535#1724797, @labath wrote:

.. Given that this code is python3 specific and other platforms still support python2, maybe we can make this bump windows-specific at first, and then extend it to other platforms once we officially stop supporting python2 ?

Yes, please. It's a mess on Windows, so I'll support a Windows-specific version bump.

[compnerd]

Use @labath's suggestion of bumping minimum required version for Windows

[labath]

This looks fine to me, and it's really great to get rid of the that code, but it would be good for some some "windows person" to ack this too. I'm particularly interested in Stella's opinion, as according to http://lab.llvm.org:8011/buildslaves/win-py3-buildbot, her bot still runs cmake 3.11. @stella.stamenova, would it be possible to upgrade that bot to cmake>=3.13 ?

[compnerd]

@stella.stamenova ping

[stella.stamenova]

Sorry, I was out on vacation until today :).

The bot is actually running 3.14 already, I updated the host file to reflect that.

[compnerd]

GIT 2046d72e916

lldb/CMakeLists.txt

 cmake_minimum_required(VERSION 3.4.3)
+if(CMAKE_SYSTEM_NAME STREQUAL Windows)
+  cmake_minimum_required(VERSION 3.13)
+endif()
 
 if(POLICY CMP0075)
   cmake_policy(SET CMP0075 NEW)

lldb/cmake/modules/LLDBConfig.cmake

   set(${OUT_VERSION_VARNAME}  ${PYTHON_VERSION_OUTPUT} PARENT_SCOPE)
 endfunction()
 
-function(find_python_libs_windows)
-  if ("${PYTHON_HOME}" STREQUAL "")
-    message(WARNING "LLDB embedded Python on Windows requires specifying a value for PYTHON_HOME.  Python support disabled.")
-    set(LLDB_DISABLE_PYTHON 1 PARENT_SCOPE)
-    return()
-  endif()
-
-  file(TO_CMAKE_PATH "${PYTHON_HOME}/Include" PYTHON_INCLUDE_DIR)
-
-  if(EXISTS "${PYTHON_INCLUDE_DIR}/patchlevel.h")
-    file(STRINGS "${PYTHON_INCLUDE_DIR}/patchlevel.h" python_version_str
-         REGEX "^#define[ \t]+PY_VERSION[ \t]+\"[^\"]+\"")
-    string(REGEX REPLACE "^#define[ \t]+PY_VERSION[ \t]+\"([^\"+]+)[+]?\".*" "\\1"
-         PYTHONLIBS_VERSION_STRING "${python_version_str}")
-    message(STATUS "Found Python library version ${PYTHONLIBS_VERSION_STRING}")
-    string(REGEX REPLACE "([0-9]+)[.]([0-9]+)[.][0-9]+" "python\\1\\2" PYTHONLIBS_BASE_NAME "${PYTHONLIBS_VERSION_STRING}")
-    unset(python_version_str)
-  else()
-    message(WARNING "Unable to find ${PYTHON_INCLUDE_DIR}/patchlevel.h, Python installation is corrupt.")
-    message(WARNING "Python support will be disabled for this build.")
-    set(LLDB_DISABLE_PYTHON 1 PARENT_SCOPE)
-    return()
-  endif()
-
-  file(TO_CMAKE_PATH "${PYTHON_HOME}" PYTHON_HOME)
-  # TODO(compnerd) when CMake Policy `CMP0091` is set to NEW, we should use
-  # if(CMAKE_MSVC_RUNTIME_LIBRARY MATCHES MultiThreadedDebug)
-  if(NOT DEFINED CMAKE_BUILD_TYPE)
-    # Multi-target generator was selected (like Visual Studio or Xcode) where no concrete build type was passed
-    # Lookup for both debug and release python installations
-    find_python_libs_windows_helper(TRUE  PYTHON_DEBUG_EXE   PYTHON_DEBUG_LIB   PYTHON_DEBUG_DLL   PYTHON_DEBUG_VERSION_STRING)
-    find_python_libs_windows_helper(FALSE PYTHON_RELEASE_EXE PYTHON_RELEASE_LIB PYTHON_RELEASE_DLL PYTHON_RELEASE_VERSION_STRING)
-    if(LLDB_DISABLE_PYTHON)
-      set(LLDB_DISABLE_PYTHON 1 PARENT_SCOPE)
-      return()
-    endif()
-
-    # We should have been found both debug and release python here
-    # Now check that their versions are equal
-    if(NOT PYTHON_DEBUG_VERSION_STRING STREQUAL PYTHON_RELEASE_VERSION_STRING)
-      message(FATAL_ERROR "Python versions for debug (${PYTHON_DEBUG_VERSION_STRING}) and release (${PYTHON_RELEASE_VERSION_STRING}) are different."
-                          "Python installation is corrupted")
-    endif ()
-
-    set(PYTHON_EXECUTABLE $<$<CONFIG:Debug>:${PYTHON_DEBUG_EXE}>$<$<NOT:$<CONFIG:Debug>>:${PYTHON_RELEASE_EXE}>)
-    set(PYTHON_LIBRARY    $<$<CONFIG:Debug>:${PYTHON_DEBUG_LIB}>$<$<NOT:$<CONFIG:Debug>>:${PYTHON_RELEASE_LIB}>)
-    set(PYTHON_DLL        $<$<CONFIG:Debug>:${PYTHON_DEBUG_DLL}>$<$<NOT:$<CONFIG:Debug>>:${PYTHON_RELEASE_DLL}>)
-    set(PYTHON_VERSION_STRING ${PYTHON_RELEASE_VERSION_STRING})
-  else()
-    # Lookup for concrete python installation depending on build type
-    if (CMAKE_BUILD_TYPE STREQUAL Debug)
-      set(LOOKUP_DEBUG_PYTHON TRUE)
-    else()
-      set(LOOKUP_DEBUG_PYTHON FALSE)
-    endif()
-    find_python_libs_windows_helper(${LOOKUP_DEBUG_PYTHON} PYTHON_EXECUTABLE PYTHON_LIBRARY PYTHON_DLL PYTHON_VERSION_STRING)
-    if(LLDB_DISABLE_PYTHON)
-      set(LLDB_DISABLE_PYTHON 1 PARENT_SCOPE)
-      return()
-    endif()
-  endif()
-
-  if(PYTHON_VERSION_STRING)
-    string(REPLACE "." ";" PYTHON_VERSION_PARTS "${PYTHON_VERSION_STRING}")
-    list(GET PYTHON_VERSION_PARTS 0 PYTHON_VERSION_MAJOR)
-    list(GET PYTHON_VERSION_PARTS 1 PYTHON_VERSION_MINOR)
-    list(GET PYTHON_VERSION_PARTS 2 PYTHON_VERSION_PATCH)
-  else()
-    unset(PYTHON_VERSION_MAJOR)
-    unset(PYTHON_VERSION_MINOR)
-    unset(PYTHON_VERSION_PATCH)
-  endif()
-
-  # Set the same variables as FindPythonInterp and FindPythonLibs.
-  set(PYTHON_EXECUTABLE         "${PYTHON_EXECUTABLE}"          CACHE PATH "")
-  set(PYTHON_LIBRARY            "${PYTHON_LIBRARY}"             CACHE PATH "")
-  set(PYTHON_DLL                "${PYTHON_DLL}"                 CACHE PATH "")
-  set(PYTHON_INCLUDE_DIR        "${PYTHON_INCLUDE_DIR}"         CACHE PATH "")
-  set(PYTHONLIBS_VERSION_STRING "${PYTHONLIBS_VERSION_STRING}"  PARENT_SCOPE)
-  set(PYTHON_VERSION_STRING     "${PYTHON_VERSION_STRING}"      PARENT_SCOPE)
-  set(PYTHON_VERSION_MAJOR      "${PYTHON_VERSION_MAJOR}"       PARENT_SCOPE)
-  set(PYTHON_VERSION_MINOR      "${PYTHON_VERSION_MINOR}"       PARENT_SCOPE)
-  set(PYTHON_VERSION_PATCH      "${PYTHON_VERSION_PATCH}"       PARENT_SCOPE)
-
-  message(STATUS "LLDB Found PythonExecutable: ${PYTHON_EXECUTABLE} (${PYTHON_VERSION_STRING})")
-  message(STATUS "LLDB Found PythonLibs: ${PYTHON_LIBRARY} (${PYTHONLIBS_VERSION_STRING})")
-  message(STATUS "LLDB Found PythonDLL: ${PYTHON_DLL}")
-  message(STATUS "LLDB Found PythonIncludeDirs: ${PYTHON_INCLUDE_DIR}")
-endfunction(find_python_libs_windows)
-
-# Call find_python_libs_windows ahead of the rest of the python configuration.
-# It's possible that it won't find a python installation and will then set
-# LLDB_DISABLE_PYTHON to ON.
-if (NOT LLDB_DISABLE_PYTHON AND "${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
-  find_python_libs_windows()
-endif()
-
 if (NOT LLDB_DISABLE_PYTHON)
   if ("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
+    find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
+    if(Python3_VERSION VERSION_LESS 3.5)
+      message(FATAL_ERROR "Python 3.5 or newer is required (found: ${Python3_VERSION})")
+    endif()
+    set(PYTHON_LIBRARY ${Python3_LIBRARIES})
+    include_directories(${Python3_INCLUDE_DIRS})
+
     if (NOT LLDB_RELOCATABLE_PYTHON)
       file(TO_CMAKE_PATH "${PYTHON_HOME}" LLDB_PYTHON_HOME)
       add_definitions( -DLLDB_PYTHON_HOME="${LLDB_PYTHON_HOME}" )