Addressed comments:

- fix comments
- add a LIT test case
- will put driver-by fix to remove dlclose() in a separate PR

Author: xingxue-ibm

libunwind/src/UnwindCursor.hpp

@@ -2129,12 +2129,12 @@ bool UnwindCursor<A, R>::getInfoFromTBTable(pint_t pc, R &registers) {
     // libunwind on libc++abi in cases such as non-C++ applications.
 
     // Resolve the function pointer to the state table personality if it has
-    // not already done.
+    // not already been done.
     if (xlcPersonalityV0 == NULL) {
       xlcPersonalityV0InitLock.lock();
       if (xlcPersonalityV0 == NULL) {
         // Resolve __xlcxx_personality_v0 using dlopen().
-        const char libcxxabi[] = "libc++abi.a(libc++abi.so.1)";
+        const char *libcxxabi = "libc++abi.a(libc++abi.so.1)";
         void *libHandle;
         // The AIX dlopen() sets errno to 0 when it is successful, which
         // clobbers the value of errno from the user code. This is an AIX
@@ -2152,6 +2152,7 @@ bool UnwindCursor<A, R>::getInfoFromTBTable(pint_t pc, R &registers) {
           _LIBUNWIND_TRACE_UNWINDING("dlsym() failed with errno=%d\n", errno);
           assert(0 && "dlsym() failed");
         }
+        dlclose(libHandle);
         errno = saveErrno;
       }
       xlcPersonalityV0InitLock.unlock();

libunwind/test/aix_runtime_link.pass.cpp

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Test that libunwind loads successfully independently of libc++abi with
+// runtime linking on AIX.
+
+// REQUIRES: target={{.+}}-aix{{.*}}
+// ADDITIONAL_COMPILE_FLAGS: -Wl,-brtl
+
+#include <unwind.h>
+extern "C" int printf(const char *, ...);
+int main(void) {
+  void *fp = (void *)&_Unwind_Backtrace;
+  printf("%p\n", fp);
+}