[lldb] Check SafeToCallFunctions before calling functions in GetExceptionObjectForThread

[aprantl]

A testcase that triggers this situation would be nice, too.

source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp

558

I recently started writing these early-exit returns as return {};

[kubamracek]

I recently started writing these early-exit returns as return {};

Good suggestion!

A testcase that triggers this situation would be nice, too.

I think this is too tricky. If I understand correctly, an example of an unsafe-to-call thread state is when we're parked inside a __select system call, and if we do invoke other code on that thread, sometimes, some kernel data structures can get out of sync from the thread state and the __select system call can sometimes return wrong results. Sounds quite hard to write a reliable test case for this, since the exact behavior also depends on OS version. I hope you'll forgive me for not providing this test :)

source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp

bool ItaniumABILanguageRuntime::ExceptionBreakpointsExplainStop(
 
   uint64_t break_site_id = stop_reason->GetValue();
   return m_process->GetBreakpointSiteList().BreakpointSiteContainsBreakpoint(
       break_site_id, m_cxx_exception_bp_sp->GetID());
 }
 
 ValueObjectSP ItaniumABILanguageRuntime::GetExceptionObjectForThread(
     ThreadSP thread_sp) {
+  if (!thread_sp->SafeToCallFunctions())
+    return {};
+
   ClangASTContext *clang_ast_context =
       m_process->GetTarget().GetScratchClangASTContext();
   CompilerType voidstar =
       clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
 
   DiagnosticManager diagnostics;
   ExecutionContext exe_ctx;
   EvaluateExpressionOptions options;