Reapply r250906 with many suggested updates from Rafael Espindola.

The needed lld matching changes to be submitted immediately next,
but this revision will cause lld failures with this alone which is expected.

This removes the eating of the error in Archive::Child::getSize() when the characters
in the size field in the archive header for the member is not a number.  To do this we
have all of the needed methods return ErrorOr to push them up until we get out of lib.
Then the tools and can handle the error in whatever way is appropriate for that tool.

So the solution is to plumb all the ErrorOr stuff through everything that touches archives.
This include its iterators as one can create an Archive object but the first or any other
Child object may fail to be created due to a bad size field in its header.

Thanks to Lang Hames on the changes making child_iterator contain an
ErrorOr<Child> instead of a Child and the needed changes to ErrorOr.h to add
operator overloading for * and -> .

We don’t want to use llvm_unreachable() as it calls abort() and is produces a “crash”
and using report_fatal_error() to move the error checking will cause the program to
stop, neither of which are really correct in library code. There are still some uses of
these that should be cleaned up in this library code for other than the size field.

The test cases use archives with text files so one can see the non-digit character,
in this case a ‘%’, in the size field.

These changes will require corresponding changes to the lld project.  That will be
committed immediately after this change.  But this revision will cause lld failures
with this alone which is expected.

llvm-svn: 252192

2 files changed, 27 insertions, 10 deletions

diff --git a/llvm/include/llvm/Object/Archive.h b/llvm/include/llvm/Object/Archive.h
index bd1be994e18..a68f200ce3f 100644
--- a/llvm/include/llvm/Object/Archive.h
+++ b/llvm/include/llvm/Object/Archive.h
@@ -66,7 +66,7 @@ public:
     bool isThinMember() const;
 
   public:
-    Child(const Archive *Parent, const char *Start);
+    Child(const Archive *Parent, const char *Start, std::error_code *EC);
     Child(const Archive *Parent, StringRef Data, uint16_t StartOfFile);
 
     bool operator ==(const Child &other) const {
@@ -75,7 +75,7 @@ public:
     }
 
     const Archive *getParent() const { return Parent; }
-    Child getNext() const;
+    ErrorOr<Child> getNext() const;
 
     ErrorOr<StringRef> getName() const;
     StringRef getRawName() const { return getHeader()->getName(); }
@@ -91,9 +91,9 @@ public:
       return getHeader()->getAccessMode();
     }
     /// \return the size of the archive member without the header or padding.
-    uint64_t getSize() const;
+    ErrorOr<uint64_t> getSize() const;
     /// \return the size in the archive header for this member.
-    uint64_t getRawSize() const;
+    ErrorOr<uint64_t> getRawSize() const;
 
     ErrorOr<StringRef> getBuffer() const;
     uint64_t getChildOffset() const;
@@ -105,24 +105,32 @@ public:
   };
 
   class child_iterator {
-    Child child;
+    ErrorOr<Child> child;
 
   public:
-    child_iterator() : child(Child(nullptr, nullptr)) {}
+    child_iterator() : child(Child(nullptr, nullptr, nullptr)) {}
     child_iterator(const Child &c) : child(c) {}
-    const Child *operator->() const { return &child; }
-    const Child &operator*() const { return child; }
+    child_iterator(std::error_code EC) : child(EC) {}
+    const ErrorOr<Child> *operator->() const { return &child; }
+    const ErrorOr<Child> &operator*() const { return child; }
 
     bool operator==(const child_iterator &other) const {
-      return child == other.child;
+      // We ignore error states so that comparisions with end() work, which
+      // allows range loops.
+      if (child.getError() || other.child.getError())
+        return false;
+      return *child == *other.child;
     }
 
     bool operator!=(const child_iterator &other) const {
       return !(*this == other);
     }
 
+    // Code in loops with child_iterators must check for errors on each loop
+    // iteration.  And if there is an error break out of the loop.
     child_iterator &operator++() { // Preincrement
-      child = child.getNext();
+      assert(child && "Can't increment iterator with error");
+      child = child->getNext();
       return *this;
     }
   };
diff --git a/llvm/include/llvm/Support/ErrorOr.h b/llvm/include/llvm/Support/ErrorOr.h
index 46b61921775..ca6ede73e8d 100644
--- a/llvm/include/llvm/Support/ErrorOr.h
+++ b/llvm/include/llvm/Support/ErrorOr.h
@@ -91,6 +91,7 @@ private:
   typedef typename std::remove_reference<T>::type &reference;
   typedef const typename std::remove_reference<T>::type &const_reference;
   typedef typename std::remove_reference<T>::type *pointer;
+  typedef const typename std::remove_reference<T>::type *const_pointer;
 
 public:
   template <class E>
@@ -183,10 +184,14 @@ public:
     return toPointer(getStorage());
   }
 
+  const_pointer operator->() const { return toPointer(getStorage()); }
+
   reference operator *() {
     return *getStorage();
   }
 
+  const_reference operator*() const { return *getStorage(); }
+
 private:
   template <class OtherT>
   void copyConstruct(const ErrorOr<OtherT> &Other) {
@@ -246,10 +251,14 @@ private:
     return Val;
   }
 
+  const_pointer toPointer(const_pointer Val) const { return Val; }
+
   pointer toPointer(wrap *Val) {
     return &Val->get();
   }
 
+  const_pointer toPointer(const wrap *Val) const { return &Val->get(); }
+
   storage_type *getStorage() {
     assert(!HasError && "Cannot get value when an error exists!");
     return reinterpret_cast<storage_type*>(TStorage.buffer);