From 6a75d842c9e279ed5e309e7cbc15d9ff1f81ca93 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Tue, 31 Mar 2015 22:08:43 +0000
Subject: [PATCH] ELF: Fix dereferencing end() iterator.

findAbsoluteAtom() returns absoluteAtom().end() if no atom is found.
Dereferencing end() value results an undefined behavior.

llvm-svn: 233765
---
 .../ELF/Hexagon/HexagonTargetHandler.h        | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/lld/lib/ReaderWriter/ELF/Hexagon/HexagonTargetHandler.h b/lld/lib/ReaderWriter/ELF/Hexagon/HexagonTargetHandler.h
index 6c1054757ed4..290f4af41808 100644
--- a/lld/lib/ReaderWriter/ELF/Hexagon/HexagonTargetHandler.h
+++ b/lld/lib/ReaderWriter/ELF/Hexagon/HexagonTargetHandler.h
@@ -30,8 +30,7 @@ public:
   };
 
   HexagonTargetLayout(HexagonLinkingContext &hti)
-      : TargetLayout<HexagonELFType>(hti), _sdataSection(nullptr),
-        _gotSymAtom(nullptr), _cachedGotSymAtom(false) {
+      : TargetLayout<HexagonELFType>(hti), _sdataSection() {
     _sdataSection = new (_alloc) SDataSection<HexagonELFType>(hti);
   }
 
@@ -84,21 +83,19 @@ public:
   }
 
   uint64_t getGOTSymAddr() {
-    if (!_cachedGotSymAtom) {
-      auto gotAtomIter = this->findAbsoluteAtom("_GLOBAL_OFFSET_TABLE_");
-      _gotSymAtom = (*gotAtomIter);
-      _cachedGotSymAtom = true;
+    if (!_gotSymAtom.hasValue()) {
+      auto iter = this->findAbsoluteAtom("_GLOBAL_OFFSET_TABLE_");
+      _gotSymAtom = (iter == this->absoluteAtoms().end()) ? nullptr : *iter;
     }
-    if (_gotSymAtom)
-      return _gotSymAtom->_virtualAddr;
+    if (*_gotSymAtom)
+      return (*_gotSymAtom)->_virtualAddr;
     return 0;
   }
 
 private:
   llvm::BumpPtrAllocator _alloc;
-  SDataSection<HexagonELFType> *_sdataSection;
-  AtomLayout *_gotSymAtom;
-  bool _cachedGotSymAtom;
+  SDataSection<HexagonELFType> *_sdataSection = nullptr;
+  llvm::Optional<AtomLayout *> _gotSymAtom;
 };
 
 /// \brief TargetHandler for Hexagon