[lldb/python] Fix (some) dangling pointers in our glue code

This starts to fix the other half of the lifetime problems in this code
-- dangling references. SB objects created on the stack will go away
when the function returns, which is a problem if the python code they
were meant for stashes a reference to them somewhere.  Most of the time
this goes by unnoticed, as the code rarely has a reason to store these,
but in case it does, we shouldn't respond by crashing.

This patch fixes the management for a couple of SB objects (Debugger,
Frame, Thread). The SB objects are now created on the heap, and
their ownership is immediately passed on to SWIG, which will ensure they
are destroyed when the last python reference goes away. I will handle
the other objects in separate patches.

I include one test which demonstrates the lifetime issue for SBDebugger.
Strictly speaking, one should create a test case for each of these
objects and each of the contexts they are being used. That would require
figuring out how to persist (and later access) each of these objects.
Some of those may involve a lot of hoop-jumping (we can run python code
from within a frame-format string). I don't think that is
necessary/worth it since the new wrapper functions make it very hard to
get this wrong.

Differential Revision: https://reviews.llvm.org/D115925

1 files changed, 10 insertions, 10 deletions

diff --git a/lldb/unittests/ScriptInterpreter/Python/PythonTestSuite.cpp b/lldb/unittests/ScriptInterpreter/Python/PythonTestSuite.cpp
index c27fc03..837f6cb 100644
--- a/lldb/unittests/ScriptInterpreter/Python/PythonTestSuite.cpp
+++ b/lldb/unittests/ScriptInterpreter/Python/PythonTestSuite.cpp
@@ -88,7 +88,7 @@ void *lldb_private::LLDBSwigPythonCreateSyntheticProvider(
 
 void *lldb_private::LLDBSwigPythonCreateCommandObject(
     const char *python_class_name, const char *session_dictionary_name,
-    const lldb::DebuggerSP debugger_sp) {
+    lldb::DebuggerSP debugger_sp) {
   return nullptr;
 }
 
@@ -172,14 +172,14 @@ PyObject *lldb_private::LLDBSwigPython_GetValueSynthProviderInstance(
 
 bool lldb_private::LLDBSwigPythonCallCommand(
     const char *python_function_name, const char *session_dictionary_name,
-    lldb::DebuggerSP &debugger, const char *args,
+    lldb::DebuggerSP debugger, const char *args,
     lldb_private::CommandReturnObject &cmd_retobj,
     lldb::ExecutionContextRefSP exe_ctx_ref_sp) {
   return false;
 }
 
 bool lldb_private::LLDBSwigPythonCallCommandObject(
-    PyObject *implementor, lldb::DebuggerSP &debugger, const char *args,
+    PyObject *implementor, lldb::DebuggerSP debugger, const char *args,
     lldb_private::CommandReturnObject &cmd_retobj,
     lldb::ExecutionContextRefSP exe_ctx_ref_sp) {
   return false;
@@ -187,7 +187,7 @@ bool lldb_private::LLDBSwigPythonCallCommandObject(
 
 bool lldb_private::LLDBSwigPythonCallModuleInit(
     const char *python_module_name, const char *session_dictionary_name,
-    lldb::DebuggerSP &debugger) {
+    lldb::DebuggerSP debugger) {
   return false;
 }
 
@@ -228,10 +228,10 @@ bool lldb_private::LLDBSWIGPythonRunScriptKeywordProcess(
   return false;
 }
 
-bool lldb_private::LLDBSWIGPythonRunScriptKeywordThread(
+llvm::Optional<std::string> lldb_private::LLDBSWIGPythonRunScriptKeywordThread(
     const char *python_function_name, const char *session_dictionary_name,
-    lldb::ThreadSP &thread, std::string &output) {
-  return false;
+    lldb::ThreadSP thread) {
+  return llvm::None;
 }
 
 bool lldb_private::LLDBSWIGPythonRunScriptKeywordTarget(
@@ -240,10 +240,10 @@ bool lldb_private::LLDBSWIGPythonRunScriptKeywordTarget(
   return false;
 }
 
-bool lldb_private::LLDBSWIGPythonRunScriptKeywordFrame(
+llvm::Optional<std::string> lldb_private::LLDBSWIGPythonRunScriptKeywordFrame(
     const char *python_function_name, const char *session_dictionary_name,
-    lldb::StackFrameSP &frame, std::string &output) {
-  return false;
+    lldb::StackFrameSP frame) {
+  return llvm::None;
 }
 
 bool lldb_private::LLDBSWIGPythonRunScriptKeywordValue(