[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).

llvm-svn: 275316

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index bb171ec3fc3..8414239cb50 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -1702,10 +1702,8 @@ static void DumpObject(const ObjectFile *o, const Archive *a = nullptr) {
 
 /// @brief Dump each object file in \a a;
 static void DumpArchive(const Archive *a) {
-  for (auto &ErrorOrChild : a->children()) {
-    if (std::error_code EC = ErrorOrChild.getError())
-      report_error(a->getFileName(), EC);
-    const Archive::Child &C = *ErrorOrChild;
+  Error Err;
+  for (auto &C : a->children(Err)) {
     Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
     if (!ChildOrErr) {
       if (auto E = isNotObjectErrorInvalidFileType(ChildOrErr.takeError()))
@@ -1717,6 +1715,8 @@ static void DumpArchive(const Archive *a) {
     else
       report_error(a->getFileName(), object_error::invalid_file_type);
   }
+  if (Err)
+    report_error(a->getFileName(), std::move(Err));
 }
 
 /// @brief Open file and figure out how to dump it.