commit c1793813f37be06517dd5b8b5f92f8d61fc78f04
author Martin Storsjö <martin@martin.st> Tue Apr 18 15:42:35 2023 +0300
committer Copybara-Service <copybara-worker@google.com> Sat Apr 22 12:55:40 2023 -0700
tree 4736636e2f84f273c9536cb40a572ecbb9265e25
parent 10ea972730a9050a7f2eb19e49bf34bb525cbb01

[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

GitOrigin-RevId: f6320f5e0e63268049086d17e903ee9bc80a996d

src/UnwindCursor.hpp

diff --git a/src/UnwindCursor.hpp b/src/UnwindCursor.hpp
index 8b6451c..db6d0ec 100644
--- a/src/UnwindCursor.hpp
+++ b/src/UnwindCursor.hpp
@@ -575,6 +575,7 @@
                 "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<> 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;