[libunwind] [SEH] Handle ExceptionContinueExecution in forced unwinding

mstorsjo · mstorsjo · commit 66632e879814 · 2023-04-11T00:00:30.000+03:00
This fixes the libcxxabi test force_unwind3.pass.cpp when run on native Windows. When unwinding past the main thread function into the system functions that brought up the thread, we can hit functions whose personality functions return ExceptionContinueExecution (instead of the regular ExceptionContinueSearch). Interpret this as a signal to stop the unwind. Curiously, in this case, it does return ExceptionContinueSearch if running within a debugger. Differential Revision: https://reviews.llvm.org/D147739
diff --git a/libunwind/src/Unwind-seh.cpp b/libunwind/src/Unwind-seh.cpp
@@ -217,6 +217,7 @@ __libunwind_seh_personality(int version, _Unwind_Action state,
                                                            disp_ctx->ContextRecord,
                                                            disp_ctx);
   switch (ms_act) {
+  case ExceptionContinueExecution: return _URC_END_OF_STACK;
   case ExceptionContinueSearch: return _URC_CONTINUE_UNWIND;
   case 4 /*ExceptionExecuteHandler*/:
     return phase2 ? _URC_INSTALL_CONTEXT : _URC_HANDLER_FOUND;
@@ -304,6 +305,12 @@ unwind_phase2_forced(unw_context_t *uc,
         // We may get control back if landing pad calls _Unwind_Resume().
         __unw_resume(&cursor2);
         break;
+      case _URC_END_OF_STACK:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
+                                   "personality returned "
+                                   "_URC_END_OF_STACK",
+                                   (void *)exception_object);
+        break;
       default:
         // Personality routine returned an unknown result code.
         _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
@@ -312,6 +319,8 @@ unwind_phase2_forced(unw_context_t *uc,
                                    (void *)exception_object, personalityResult);
         return _URC_FATAL_PHASE2_ERROR;
       }
+      if (personalityResult == _URC_END_OF_STACK)
+        break;
     }
   }
 
