[libunwind] f6320f5 - [libunwind] [SEH] Clear DISPATCHER_CONTEXT when initializing a cursor

[Martin Storsjö via cfe-commits]

Author: Martin Storsjö
Date: 2023-04-22T22:47:45+03:00
New Revision: f6320f5e0e63268049086d17e903ee9bc80a996d

URL: https://github.com/llvm/llvm-project/commit/f6320f5e0e63268049086d17e903ee9bc80a996d
DIFF: https://github.com/llvm/llvm-project/commit/f6320f5e0e63268049086d17e903ee9bc80a996d.diff

LOG: [libunwind] [SEH] Clear DISPATCHER_CONTEXT when initializing a cursor

We only initialize a few fields in DISPATCHER_CONTEXT - don't leave
the rest in an uninitialized state; make sure the whole struct is
in a deterministic state.

This makes nondeterministic failures deterministic, for some cases
relating to forced unwinding on aarch64/arm (which requires filling
in parsing of the xdata for finding the exception handler and LSDA).

Differential Revision: https://reviews.llvm.org/D148660

Added: 
    

Modified: 
    libunwind/src/UnwindCursor.hpp

Removed: 
    


################################################################################
diff  --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
index 8b6451c68b46..db6d0ec853f3 100644
--- a/libunwind/src/UnwindCursor.hpp
+++ b/libunwind/src/UnwindCursor.hpp
@@ -575,6 +575,7 @@ UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as)
                 "UnwindCursor<> requires more alignment than unw_cursor_t");
   memset(&_info, 0, sizeof(_info));
   memset(&_histTable, 0, sizeof(_histTable));
+  memset(&_dispContext, 0, sizeof(_dispContext));
   _dispContext.ContextRecord = &_msContext;
   _dispContext.HistoryTable = &_histTable;
   // Initialize MS context from ours.
@@ -677,6 +678,7 @@ UnwindCursor<A, R>::UnwindCursor(CONTEXT *context, A &as)
                 "UnwindCursor<> does not fit in unw_cursor_t");
   memset(&_info, 0, sizeof(_info));
   memset(&_histTable, 0, sizeof(_histTable));
+  memset(&_dispContext, 0, sizeof(_dispContext));
   _dispContext.ContextRecord = &_msContext;
   _dispContext.HistoryTable = &_histTable;
   _msContext = *context;