From bf0e75a50e035fa441200d62f3a78a7edf8fe45f Mon Sep 17 00:00:00 2001
From: Chris Bieneman <beanz@apple.com>
Date: Fri, 20 May 2016 20:15:17 +0000
Subject: Revert "Work around a glibc bug: backtrace() spuriously fails if..."

This commit has been breaking the FreeBSD bots:
http://lab.llvm.org:8011/builders/lld-x86_64-freebsd

This reverts commit r269992.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270267 91177308-0d34-0410-b5e6-96231b3b80d8
---
 cmake/config-ix.cmake        |  1 -
 lib/Support/Unix/Signals.inc | 55 ++++----------------------------------------
 2 files changed, 4 insertions(+), 52 deletions(-)

diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index b3f225f0740..7d5277517a9 100755
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -144,7 +144,6 @@ endif()
 # function checks
 check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
 check_symbol_exists(backtrace "execinfo.h" HAVE_BACKTRACE)
-check_symbol_exists(_Unwind_Backtrace "unwind.h" HAVE_UNWIND_BACKTRACE)
 check_symbol_exists(getpagesize unistd.h HAVE_GETPAGESIZE)
 check_symbol_exists(getrusage sys/resource.h HAVE_GETRUSAGE)
 check_symbol_exists(setrlimit sys/resource.h HAVE_SETRLIMIT)
diff --git a/lib/Support/Unix/Signals.inc b/lib/Support/Unix/Signals.inc
index 27f3414ce57..061cdb3da21 100644
--- a/lib/Support/Unix/Signals.inc
+++ b/lib/Support/Unix/Signals.inc
@@ -45,9 +45,6 @@
 #if HAVE_LINK_H
 #include <link.h>
 #endif
-#if HAVE_UNWIND_BACKTRACE
-#include <unwind.h>
-#endif
 
 using namespace llvm;
 
@@ -312,61 +309,17 @@ static bool findModulesAndOffsets(void **StackTrace, int Depth,
 }
 #endif // defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES) && ...
 
-#if defined(ENABLE_BACKTRACES) && defined(HAVE_UNWIND_BACKTRACE)
-static int unwindBacktrace(void **StackTrace, int MaxEntries) {
-  if (MaxEntries < 0)
-    return 0;
-
-  // Skip the first frame ('unwindBacktrace' itself).
-  int Entries = -1;
-
-  auto HandleFrame = [&](_Unwind_Context *Context) -> _Unwind_Reason_Code {
-    // Apparently we need to detect reaching the end of the stack ourselves.
-    void *IP = (void *)_Unwind_GetIP(Context);
-    if (!IP)
-      return _URC_END_OF_STACK;
-
-    assert(Entries < MaxEntries && "recursively called after END_OF_STACK?");
-    if (Entries >= 0)
-      StackTrace[Entries] = IP;
-
-    if (++Entries == MaxEntries)
-      return _URC_END_OF_STACK;
-    return _URC_NO_REASON;
-  };
-
-  _Unwind_Backtrace(
-      [](_Unwind_Context *Context, void *Handler) {
-        return (*static_cast<decltype(HandleFrame) *>(Handler))(Context);
-      },
-      static_cast<void *>(&HandleFrame));
-  return std::max(Entries, 0);
-}
-#endif
-
 // PrintStackTrace - In the case of a program crash or fault, print out a stack
 // trace so that the user has an indication of why and where we died.
 //
 // On glibc systems we have the 'backtrace' function, which works nicely, but
 // doesn't demangle symbols.
 void llvm::sys::PrintStackTrace(raw_ostream &OS) {
-#if defined(ENABLE_BACKTRACES)
-  static void *StackTrace[256];
-  int depth = 0;
-#if defined(HAVE_BACKTRACE)
+#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
+  static void* StackTrace[256];
   // Use backtrace() to output a backtrace on Linux systems with glibc.
-  if (!depth)
-    depth = backtrace(StackTrace, static_cast<int>(array_lengthof(StackTrace)));
-#endif
-#if defined(HAVE_UNWIND_BACKTRACE)
-  // Try _Unwind_Backtrace() if backtrace() failed.
-  if (!depth)
-    depth = unwindBacktrace(StackTrace,
+  int depth = backtrace(StackTrace,
                         static_cast<int>(array_lengthof(StackTrace)));
-#endif
-  if (!depth)
-    return;
-
   if (printSymbolizedStackTrace(StackTrace, depth, OS))
     return;
 #if HAVE_DLFCN_H && __GNUG__
@@ -416,7 +369,7 @@ void llvm::sys::PrintStackTrace(raw_ostream &OS) {
     }
     OS << '\n';
   }
-#elif defined(HAVE_BACKTRACE)
+#else
   backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
 #endif
 #endif
-- 
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