Allow customized relative PYTHONHOME (Attemp 1)

[hhb]

Summary

This is another attempt of 0bb90628b5f7c170689d2d3f019af773772fc649.

The difference is that g_python_home is not declared as const. Since
some versions of python do not expect that.

lldb/cmake/modules/LLDBConfig.cmake

 
 add_optional_dependency(LLDB_ENABLE_LIBEDIT "Enable editline support in LLDB" LibEdit LibEdit_FOUND)
 add_optional_dependency(LLDB_ENABLE_CURSES "Enable curses support in LLDB" CursesAndPanel CURSESANDPANEL_FOUND)
 add_optional_dependency(LLDB_ENABLE_LZMA "Enable LZMA compression support in LLDB" LibLZMA LIBLZMA_FOUND)
 add_optional_dependency(LLDB_ENABLE_LUA "Enable Lua scripting support in LLDB" LuaAndSwig LUAANDSWIG_FOUND)
 add_optional_dependency(LLDB_ENABLE_PYTHON "Enable Python scripting support in LLDB" PythonInterpAndLibs PYTHONINTERPANDLIBS_FOUND)
 add_optional_dependency(LLDB_ENABLE_LIBXML2 "Enable Libxml 2 support in LLDB" LibXml2 LIBXML2_FOUND VERSION 2.8)
 
-option(LLDB_RELOCATABLE_PYTHON "Use the PYTHONHOME environment variable to locate Python." OFF)
 option(LLDB_USE_SYSTEM_SIX "Use six.py shipped with system and do not install a copy of it" OFF)
 option(LLDB_USE_ENTITLEMENTS "When codesigning, use entitlements if available" ON)
 option(LLDB_BUILD_FRAMEWORK "Build LLDB.framework (Darwin only)" OFF)
 option(LLDB_NO_INSTALL_DEFAULT_RPATH "Disable default RPATH settings in binaries" OFF)
 option(LLDB_USE_SYSTEM_DEBUGSERVER "Use the system's debugserver for testing (Darwin only)." OFF)
 option(LLDB_SKIP_STRIP "Whether to skip stripping of binaries when installing lldb." OFF)
 
 if (LLDB_USE_SYSTEM_DEBUGSERVER)
else()
     set(LLDB_HAVE_EL_RFUNC_T 1)
   endif()
   set(CMAKE_REQUIRED_LIBRARIES)
   set(CMAKE_REQUIRED_INCLUDES)
   set(CMAKE_EXTRA_INCLUDE_FILES)
 endif()
 
 if (LLDB_ENABLE_PYTHON)
+  if(CMAKE_SYSTEM_NAME MATCHES "Windows")
+    set(default_embed_python_home ON)
+  else()
+    set(default_embed_python_home OFF)
+  endif()
+  option(LLDB_EMBED_PYTHON_HOME
+    "Embed PYTHONHOME in the binary. If set to OFF, PYTHONHOME environment variable will be used to to locate Python."
+    ${default_embed_python_home})
+
   include_directories(${PYTHON_INCLUDE_DIRS})
-  if ("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows" AND NOT LLDB_RELOCATABLE_PYTHON)
+  if (LLDB_EMBED_PYTHON_HOME)
     get_filename_component(PYTHON_HOME "${PYTHON_EXECUTABLE}" DIRECTORY)
-    file(TO_CMAKE_PATH "${PYTHON_HOME}" LLDB_PYTHON_HOME)
+    set(LLDB_PYTHON_HOME "${PYTHON_HOME}" CACHE STRING
+      "Path to use as PYTHONHOME in lldb. If a relative path is specified, it will be resolved at runtime relative to liblldb directory.")
   endif()
 endif()
 
 if (LLVM_EXTERNAL_CLANG_SOURCE_DIR)
   include_directories(${LLVM_EXTERNAL_CLANG_SOURCE_DIR}/include)
 else ()
   include_directories(${CMAKE_SOURCE_DIR}/tools/clang/include)
 endif ()

lldb/include/lldb/Host/Config.h.cmake

 #cmakedefine01 LLDB_ENABLE_LIBEDIT
 
 #cmakedefine01 LLDB_ENABLE_LIBXML2
 
 #cmakedefine01 LLDB_ENABLE_LUA
 
 #cmakedefine01 LLDB_ENABLE_PYTHON
 
+#cmakedefine01 LLDB_EMBED_PYTHON_HOME
+
 #cmakedefine LLDB_PYTHON_HOME "${LLDB_PYTHON_HOME}"
 
 #define LLDB_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}"
 
 #endif // #ifndef LLDB_HOST_CONFIG_H

lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp

if (m_was_already_initialized) {
       PyEval_SaveThread();
     }
 
     m_stdin_tty_state.Restore();
   }
 
 private:
   void InitializePythonHome() {
-#if defined(LLDB_PYTHON_HOME)
+#if LLDB_EMBED_PYTHON_HOME
+#if PY_MAJOR_VERSION >= 3
+    typedef wchar_t* str_type;
+#else
+    typedef char* str_type;
+#endif
+    static str_type g_python_home = []() -> str_type {
+      const char *lldb_python_home = LLDB_PYTHON_HOME;
+      const char *absolute_python_home = nullptr;
+      llvm::SmallString<64> path;
+      if (llvm::sys::path::is_absolute(lldb_python_home)) {
+        absolute_python_home = lldb_python_home;
+      } else {
+        FileSpec spec = HostInfo::GetShlibDir();
+        if (!spec)
+          return nullptr;
+        spec.GetPath(path);
+        llvm::sys::path::append(path, lldb_python_home);
+        absolute_python_home = path.c_str();
+      }
 #if PY_MAJOR_VERSION >= 3
       size_t size = 0;
-    static wchar_t *g_python_home = Py_DecodeLocale(LLDB_PYTHON_HOME, &size);
+      return Py_DecodeLocale(absolute_python_home, &size);
 #else
-    static char g_python_home[] = LLDB_PYTHON_HOME;
+      return strdup(absolute_python_home);
 #endif
+    }();
+    if (g_python_home != nullptr) {
       Py_SetPythonHome(g_python_home);
+    }
 #else
 #if defined(__APPLE__) && PY_MAJOR_VERSION == 2 && PY_MINOR_VERSION == 7
     // For Darwin, the only Python version supported is the one shipped in the
     // OS OS and linked with lldb. Other installation of Python may have higher
     // priorities in the path, overriding PYTHONHOME and causing
     // problems/incompatibilities. In order to avoid confusion, always hardcode
     // the PythonHome to be right, as it's not going to change.
     static char path[] =