Teach CMake to find versions of Python != 2.7

[zturner]

Summary

Hi Vadim,

Would you mind taking a look at this? My CMake-fu is only level 5, so if you have any suggestions on how to improve this, let me know.

Note that I'm claiming with this revision that LLDB itself works with Python versions other than 2.7. Only that CMake can set all the variables appropriately if you point it to a different version of CMake

[enlight]

cmake/modules/LLDBConfig.cmake

109

PYTHON_LIBRARY is used in this scope later on, so it needs to be explicitly set for both this scope and the parent scope, like so:

set (PYTHON_LIBRARY $<$<CONFIG:Debug>:${PYTHON_DEBUG_LIB}>$<$<NOT:$<CONFIG:Debug>>:${PYTHON_RELEASE_LIB}>)
set (PYTHON_LIBRARY ${PYTHON_LIBRARY} PARENT_SCOPE)

112–114

I think this belongs outside this function, along with include_directories below.

117

This command will never be executed because PYTHON_LIBRARY is only set in the parent scope. However, I'd prefer include_directories() wasn't here at all, let the caller of find_python_libs_windows do that instead so that the behavior is more similar to the built-in FindPythonLibs module (which means PYTHON_INCLUDE_DIRS should be made available in the parent scope, note the extra S).

131–133

Please move these into find_python_libs_windows(), as I'll need access to the debug/release paths in order to avoid printing out the generator expressions.

cmake/modules/LLDBStandalone.cmake

51–53

The comment no longer seems accurate.

[enlight]

cmake/modules/LLDBConfig.cmake

56

This will only set LLDB_DISABLE_PYTHON inside the function, you probably want to do set (LLDB_DISABLE_PYTHON 1 PARENT_SCOPE), or set (LLDB_DISABLE_PYTHON 1 CACHE INTERNAL "") instead.

73

Ditto.

[zturner]

Updated from Vadim's comments.

[enlight]

cmake/modules/LLDBConfig.cmake

113

You missed :P

140

Can we make this if (PYTHON_INCLUDE_DIRS) instead?

[enlight]

Hi Zach,

Can you close this issue please?

[zturner]

In the future, u sually the reviewer (you in this case) does this by hitting Accept in Phabricator. I can do it this time though, no worries

cmake/modules/LLDBConfig.cmake

   add_definitions( -DLLDB_DISABLE_CURSES )
 endif()
 
+# On Windows, we can't use the normal FindPythonLibs module that comes with CMake,
+# for a number of reasons.
+# 1) Prior to MSVC 2015, it is only possible to embed Python if python itself was
+#    compiled with an identical version (and build configuration) of MSVC as LLDB.
+#    The standard algorithm does not take into account the differences between
+#    a binary release distribution of python and a custom built distribution.
+# 2) From MSVC 2015 and onwards, it is only possible to use Python 3.5 or later.
+# 3) FindPythonLibs queries the registry to locate Python, and when looking for a
+#    64-bit version of Python, since cmake.exe is a 32-bit executable, it will see
+#    a 32-bit view of the registry.  As such, it is impossible for FindPythonLibs to
+#    locate 64-bit Python libraries.
+# This function is designed to address those limitations.  Currently it only partially
+# addresses them, but it can be improved and extended on an as-needed basis.
+function(find_python_libs_windows)
+  if ("${PYTHON_HOME}" STREQUAL "")
+    message("LLDB embedded Python on Windows requires specifying a value for PYTHON_HOME.  Python support disabled.")
+    set(LLDB_DISABLE_PYTHON 1 PARENT_SCOPE)
+    return()
+  endif()
+
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/Include" PYTHON_INCLUDE_DIRS)
+
+  if(EXISTS "${PYTHON_INCLUDE_DIRS}/patchlevel.h")
+    file(STRINGS "${PYTHON_INCLUDE_DIRS}/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("-- Found Python 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("Unable to find ${PYTHON_INCLUDE_DIRS}/patchlevel.h, Python installation is corrupt.")
+    message("Python support will be disabled for this build.")
+    set(LLDB_DISABLE_PYTHON 1 PARENT_SCOPE)
+    return()
+  endif()
+
+  file(TO_CMAKE_PATH "${PYTHON_HOME}" PYTHON_HOME)
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/python_d.exe" PYTHON_DEBUG_EXE)
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/libs/${PYTHONLIBS_BASE_NAME}_d.lib" PYTHON_DEBUG_LIB)
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/${PYTHONLIBS_BASE_NAME}_d.dll" PYTHON_DEBUG_DLL)
+
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/python.exe" PYTHON_RELEASE_EXE)
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/libs/${PYTHONLIBS_BASE_NAME}.lib" PYTHON_RELEASE_LIB)
+  file(TO_CMAKE_PATH "${PYTHON_HOME}/${PYTHONLIBS_BASE_NAME}.dll" PYTHON_RELEASE_DLL)
+
+  # Generator expressions are evaluated in the context of each build configuration generated
+  # by CMake. Here we use the $<CONFIG:Debug>:VALUE logical generator expression to ensure
+  # that the debug Python library, DLL, and executable are used in the Debug build configuration.
+  #
+  # Generator expressions can be difficult to grok at first so here's a breakdown of the one
+  # used for PYTHON_LIBRARY:
+  #
+  # 1. $<CONFIG:Debug> evaluates to 1 when the Debug configuration is being generated,
+  #    or 0 in all other cases.
+  # 2. $<$<CONFIG:Debug>:${PYTHON_DEBUG_LIB}> expands to ${PYTHON_DEBUG_LIB} when the Debug
+  #    configuration is being generated, or nothing (literally) in all other cases.
+  # 3. $<$<NOT:$<CONFIG:Debug>>:${PYTHON_RELEASE_LIB}> expands to ${PYTHON_RELEASE_LIB} when
+  #    any configuration other than Debug is being generated, or nothing in all other cases.
+  # 4. The conditionals in 2 & 3 are mutually exclusive.
+  # 5. A logical expression with a conditional that evaluates to 0 yields no value at all.
+  #
+  # Due to 4 & 5 it's possible to concatenate 2 & 3 to obtain a single value specific to each
+  # build configuration. In this example the value will be ${PYTHON_DEBUG_LIB} when generating the
+  # Debug configuration, or ${PYTHON_RELEASE_LIB} when generating any other configuration.
+  # Note that it's imperative that there is no whitespace between the two expressions, otherwise
+  # CMake will insert a semicolon between the two.
+  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_EXECUTABLE ${PYTHON_EXECUTABLE} PARENT_SCOPE)
+  set (PYTHON_LIBRARY ${PYTHON_LIBRARY} PARENT_SCOPE)
+  set (PYTHON_DLL ${PYTHON_LIBRARY} PYTHON_DLL PARENT_SCOPE)
+  set (PYTHON_INCLUDE_DIRS ${PYTHON_INCLUDE_DIRS} PARENT_SCOPE)
+
+  message("-- Found PythonExecutable: ${PYTHON_EXECUTABLE}")
+  message("-- Found PythonLibs: ${PYTHON_LIBRARY}")
+  message("-- Found PythonDLL: ${PYTHON_DLL}")
+  message("-- Found PythonIncludeDirs: ${PYTHON_INCLUDE_DIRS}")
+endfunction(find_python_libs_windows)
+
 if (NOT LLDB_DISABLE_PYTHON)
   if(UNIX)
     # This is necessary for crosscompile on Ubuntu 14.04 64bit. Need a proper fix.

   endif()
 
   if ("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
-    if (NOT "${PYTHON_HOME}" STREQUAL "")
-      file(TO_CMAKE_PATH "${PYTHON_HOME}" PYTHON_HOME)
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/python_d.exe" PYTHON_DEBUG_EXE)
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/libs/python27_d.lib" PYTHON_DEBUG_LIB)
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/python27_d.dll" PYTHON_DEBUG_DLL)
-
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/python.exe" PYTHON_RELEASE_EXE)
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/libs/python27.lib" PYTHON_RELEASE_LIB)
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/python27.dll" PYTHON_RELEASE_DLL)
-
-      # Generator expressions are evaluated in the context of each build configuration generated
-      # by CMake. Here we use the $<CONFIG:Debug>:VALUE logical generator expression to ensure
-      # that the debug Python library, DLL, and executable are used in the Debug build configuration.
-      #
-      # Generator expressions can be difficult to grok at first so here's a breakdown of the one
-      # used for PYTHON_LIBRARY:
-      #
-      # 1. $<CONFIG:Debug> evaluates to 1 when the Debug configuration is being generated,
-      #    or 0 in all other cases.
-      # 2. $<$<CONFIG:Debug>:${PYTHON_DEBUG_LIB}> expands to ${PYTHON_DEBUG_LIB} when the Debug
-      #    configuration is being generated, or nothing (literally) in all other cases.
-      # 3. $<$<NOT:$<CONFIG:Debug>>:${PYTHON_RELEASE_LIB}> expands to ${PYTHON_RELEASE_LIB} when
-      #    any configuration other than Debug is being generated, or nothing in all other cases.
-      # 4. The conditionals in 2 & 3 are mutually exclusive.
-      # 5. A logical expression with a conditional that evaluates to 0 yields no value at all.
-      #
-      # Due to 4 & 5 it's possible to concatenate 2 & 3 to obtain a single value specific to each
-      # build configuration. In this example the value will be ${PYTHON_DEBUG_LIB} when generating the
-      # Debug configuration, or ${PYTHON_RELEASE_LIB} when generating any other configuration.
-      # Note that it's imperative that there is no whitespace between the two expressions, otherwise
-      # CMake will insert a semicolon between the two.
-
-      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>>:${PYTHON_RELEASE_DLL}>)
-
-      file(TO_CMAKE_PATH "${PYTHON_HOME}/Include" PYTHON_INCLUDE_DIR)
-      if (NOT LLDB_RELOCATABLE_PYTHON)
-        add_definitions( -DLLDB_PYTHON_HOME="${PYTHON_HOME}" )
-      endif()
-    else()
-      message("Embedding Python on Windows without specifying a value for PYTHON_HOME is deprecated.  Support for this will be dropped soon.")
-
-      if ("${PYTHON_INCLUDE_DIR}" STREQUAL "" OR "${PYTHON_LIBRARY}" STREQUAL "")
-        message("-- LLDB Embedded python disabled.  Embedding python on Windows requires "
-                "manually specifying PYTHON_INCLUDE_DIR *and* PYTHON_LIBRARY")
-        set(LLDB_DISABLE_PYTHON 1)
-      endif()
-    endif()
+    find_python_libs_windows()
 
-    if (PYTHON_LIBRARY)
-      message("-- Found PythonLibs: ${PYTHON_LIBRARY}")
-      include_directories(${PYTHON_INCLUDE_DIR})
+    if (NOT LLDB_RELOCATABLE_PYTHON)
+      add_definitions( -DLLDB_PYTHON_HOME="${PYTHON_HOME}" )
     endif()
-
   else()
     find_package(PythonLibs REQUIRED)
+  endif()
+  
+  if (PYTHON_LIBRARY)
     include_directories(${PYTHON_INCLUDE_DIRS})
   endif()
 endif()
 
 if (LLDB_DISABLE_PYTHON)
-  unset(PYTHON_INCLUDE_DIR)
+  unset(PYTHON_INCLUDE_DIRS)
   unset(PYTHON_LIBRARY)
   add_definitions( -DLLDB_DISABLE_PYTHON )
 endif()

cmake/modules/LLDBStandalone.cmake

   include(AddLLVM)
   include(HandleLLVMOptions)
 
-  # Verify that we can find a Python 2 interpreter.  Python 3 is unsupported.
   if (PYTHON_EXECUTABLE STREQUAL "")
-    set(Python_ADDITIONAL_VERSIONS 2.7 2.6 2.5)
+    set(Python_ADDITIONAL_VERSIONS 3.5 3.4 3.3 3.2 3.1 3.0 2.7 2.6 2.5)
     include(FindPythonInterp)
     if( NOT PYTHONINTERP_FOUND )
       message(FATAL_ERROR