Fix _Unwind_Backtrace for libc++abi built with libgcc.
Implement an undocumented _US_FORCE_UNWIND flag for force
unwinding.
git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@226820 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/unwind.h b/include/unwind.h
index ad91d25..edf5fdd 100644
--- a/include/unwind.h
+++ b/include/unwind.h
@@ -63,6 +63,8 @@
static const _Unwind_State _US_VIRTUAL_UNWIND_FRAME = 0;
static const _Unwind_State _US_UNWIND_FRAME_STARTING = 1;
static const _Unwind_State _US_UNWIND_FRAME_RESUME = 2;
+/* Undocumented flag for force unwinding. */
+static const _Unwind_State _US_FORCE_UNWIND = 8;
typedef uint32_t _Unwind_EHT_Header;
diff --git a/src/cxa_personality.cpp b/src/cxa_personality.cpp
index a67fb5c..3385ea3 100644
--- a/src/cxa_personality.cpp
+++ b/src/cxa_personality.cpp
@@ -1101,9 +1101,16 @@
_Unwind_SetGR(context, REG_UCB, reinterpret_cast<uint32_t>(unwind_exception));
#endif
+ // Check the undocumented force unwinding behavior
+ bool is_force_unwinding = state & _US_FORCE_UNWIND;
+ state &= ~_US_FORCE_UNWIND;
+
scan_results results;
switch (state) {
case _US_VIRTUAL_UNWIND_FRAME:
+ if (is_force_unwinding)
+ return continue_unwind(unwind_exception, context);
+
// Phase 1 search: All we're looking for in phase 1 is a handler that halts unwinding
scan_eh_tab(results, _UA_SEARCH_PHASE, native_exception, unwind_exception, context);
if (results.reason == _URC_HANDLER_FOUND)
@@ -1119,6 +1126,11 @@
return results.reason;
case _US_UNWIND_FRAME_STARTING:
+ // TODO: Support force unwinding in the phase 2 search.
+ // NOTE: In order to call the cleanup functions, _Unwind_ForcedUnwind()
+ // will call this personality function with (_US_FORCE_UNWIND |
+ // _US_UNWIND_FRAME_STARTING).
+
// Phase 2 search
if (unwind_exception->barrier_cache.sp == _Unwind_GetGR(context, REG_SP))
{
