[lldb] Fix double free in CommandPluginInterfaceImplementation (#131658)

The class was taking ownership of the SBCommandPluginInterface pointer
it was passed in, by wrapping it in a shared pointer. This causes a
double free in the unit test when the object is destroyed and the same
pointer gets freed once when the SBCommandPluginInterface goes away and
then again when the shared pointer hits a zero refcount.

Author: JDevlieghere

lldb/source/API/SBCommandInterpreter.cpp

@@ -77,7 +77,7 @@ class CommandPluginInterfaceImplementation : public CommandObjectParsed {
     SBDebugger debugger_sb(m_interpreter.GetDebugger().shared_from_this());
     m_backend->DoExecute(debugger_sb, command.GetArgumentVector(), sb_return);
   }
-  std::shared_ptr<lldb::SBCommandPluginInterface> m_backend;
+  lldb::SBCommandPluginInterface *m_backend;
   std::optional<std::string> m_auto_repeat_command;
 };
 } // namespace lldb_private

lldb/unittests/API/SBCommandInterpreterTest.cpp

@@ -6,24 +6,28 @@
 //
 //===----------------------------------------------------------------------===/
 
-#include "gtest/gtest.h"
-
 // Use the umbrella header for -Wdocumentation.
 #include "lldb/API/LLDB.h"
 
+#include "TestingSupport/SubsystemRAII.h"
+#include "lldb/API/SBDebugger.h"
+#include "gtest/gtest.h"
 #include <cstring>
 #include <string>
 
 using namespace lldb;
+using namespace lldb_private;
 
 class SBCommandInterpreterTest : public testing::Test {
 protected:
   void SetUp() override {
-    SBDebugger::Initialize();
-    m_dbg = SBDebugger::Create(/*source_init_files=*/false);
+    debugger = SBDebugger::Create(/*source_init_files=*/false);
   }
 
-  SBDebugger m_dbg;
+  void TearDown() override { SBDebugger::Destroy(debugger); }
+
+  SubsystemRAII<lldb::SBDebugger> subsystems;
+  SBDebugger debugger;
 };
 
 class DummyCommand : public SBCommandPluginInterface {
@@ -44,7 +48,7 @@ class DummyCommand : public SBCommandPluginInterface {
 TEST_F(SBCommandInterpreterTest, SingleWordCommand) {
   // We first test a command without autorepeat
   DummyCommand dummy("It worked");
-  SBCommandInterpreter interp = m_dbg.GetCommandInterpreter();
+  SBCommandInterpreter interp = debugger.GetCommandInterpreter();
   interp.AddCommand("dummy", &dummy, /*help=*/nullptr);
   {
     SBCommandReturnObject result;
@@ -78,7 +82,7 @@ TEST_F(SBCommandInterpreterTest, SingleWordCommand) {
 }
 
 TEST_F(SBCommandInterpreterTest, MultiWordCommand) {
-  SBCommandInterpreter interp = m_dbg.GetCommandInterpreter();
+  SBCommandInterpreter interp = debugger.GetCommandInterpreter();
   auto command = interp.AddMultiwordCommand("multicommand", /*help=*/nullptr);
   // We first test a subcommand without autorepeat
   DummyCommand subcommand("It worked again");