[Object] Change Archive::child_iterator for better interop with Error/Expected.

See http://reviews.llvm.org/D22079

Changes the Archive::child_begin and Archive::children to require a reference
to an Error. If iterator increment fails (because the archive header is
damaged) the iterator will be set to 'end()', and the error stored in the
given Error&. The Error value should be checked by the user immediately after
the loop. E.g.:

Error Err;
for (auto &C : A->children(Err)) {
  // Do something with archive child C.
}
// Check the error immediately after the loop.
if (Err)
  return Err;

Failure to check the Error will result in an abort() when the Error goes out of
scope (as guaranteed by the Error class).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275316 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 29 insertions, 17 deletions

diff --git a/include/llvm/Object/Archive.h b/include/llvm/Object/Archive.h
index 77538cb5323..f209cb32351 100644
--- a/include/llvm/Object/Archive.h
+++ b/include/llvm/Object/Archive.h
@@ -106,21 +106,20 @@ public:
   };
 
   class child_iterator {
-    ErrorOr<Child> child;
+    Child C;
+    Error *E;
 
   public:
-    child_iterator() : child(Child(nullptr, nullptr, nullptr)) {}
-    child_iterator(const Child &c) : child(c) {}
-    child_iterator(std::error_code EC) : child(EC) {}
-    const ErrorOr<Child> *operator->() const { return &child; }
-    const ErrorOr<Child> &operator*() const { return child; }
+    child_iterator() : C(Child(nullptr, nullptr, nullptr)), E(nullptr) {}
+    child_iterator(const Child &C, Error *E) : C(C), E(E) {}
+    const Child *operator->() const { return &C; }
+    const Child &operator*() const { return C; }
 
     bool operator==(const child_iterator &other) const {
-      // 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;
+      // Ignore errors here: If an error occurred during increment then getNext
+      // will have been set to child_end(), and the following comparison should
+      // do the right thing.
+      return C == other.C;
     }
 
     bool operator!=(const child_iterator &other) const {
@@ -130,8 +129,15 @@ public:
     // 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
-      assert(child && "Can't increment iterator with error");
-      child = child->getNext();
+      assert(E && "Can't increment iterator with no Error attached");
+      if (auto ChildOrErr = C.getNext())
+        C = *ChildOrErr;
+      else {
+        ErrorAsOutParameter ErrAsOutParam(*E);
+        C = C.getParent()->child_end().C;
+        *E = errorCodeToError(ChildOrErr.getError());
+        E = nullptr;
+      }
       return *this;
     }
   };
@@ -190,10 +196,11 @@ public:
   Kind kind() const { return (Kind)Format; }
   bool isThin() const { return IsThin; }
 
-  child_iterator child_begin(bool SkipInternal = true) const;
+  child_iterator child_begin(Error &Err, bool SkipInternal = true) const;
   child_iterator child_end() const;
-  iterator_range<child_iterator> children(bool SkipInternal = true) const {
-    return make_range(child_begin(SkipInternal), child_end());
+  iterator_range<child_iterator> children(Error &Err,
+                                          bool SkipInternal = true) const {
+    return make_range(child_begin(Err, SkipInternal), child_end());
   }
 
   symbol_iterator symbol_begin() const;
@@ -208,7 +215,7 @@ public:
   }
 
   // check if a symbol is in the archive
-  child_iterator findSym(StringRef name) const;
+  child_iterator findSym(Error &Err, StringRef name) const;
 
   bool hasSymbolTable() const;
   StringRef getSymbolTable() const { return SymbolTable; }
diff --git a/include/llvm/Support/Error.h b/include/llvm/Support/Error.h
index 645088ceb67..5f515a88a02 100644
--- a/include/llvm/Support/Error.h
+++ b/include/llvm/Support/Error.h
@@ -940,6 +940,11 @@ private:
   std::function<int(const Error &)> GetExitCode;
 };
 
+/// Report a serious error, calling any installed error handler. See
+/// ErrorHandling.h.
+LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err,
+                                                bool gen_crash_diag = true);
+
 } // namespace llvm
 
 #endif // LLVM_SUPPORT_ERROR_H