[PATCH] D77099: Exit unwinding early when at the top of the stack and additional info won't be found.

[Sterling Augustine via Phabricator via llvm-commits]

saugustine created this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.
saugustine added reviewers: jgorbe, mstorsjo, compnerd, miyuki, mclow.lists.

This patch follows libgcc's lead: When the return-address register is
zero, there won't be additional stack frames to examine, or gather
information about. Exit before spending time looking for something
known not to be found.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77099

Files:
  libunwind/src/UnwindCursor.hpp


Index: libunwind/src/UnwindCursor.hpp
===================================================================
--- libunwind/src/UnwindCursor.hpp
+++ libunwind/src/UnwindCursor.hpp
@@ -1848,6 +1848,12 @@
   pc &= (pint_t)~0x1;
 #endif
 
+  // Exit early if at the top of the stack.
+  if (pc == 0) {
+    _unwindInfoMissing = true;
+    return;
+  }
+
   // If the last line of a function is a "throw" the compiler sometimes
   // emits no instructions after the call to __cxa_throw.  This means
   // the return address is actually the start of the next function.


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