[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, 11 insertions, 3 deletions

diff --git a/llvm/tools/llvm-cxxdump/llvm-cxxdump.cpp b/llvm/tools/llvm-cxxdump/llvm-cxxdump.cpp
index 0c408ccb5ba..c92d20d6ccf 100644
--- a/llvm/tools/llvm-cxxdump/llvm-cxxdump.cpp
+++ b/llvm/tools/llvm-cxxdump/llvm-cxxdump.cpp
@@ -50,6 +50,14 @@ static void error(std::error_code EC) {
   exit(1);
 }
 
+static void error(Error Err) {
+  if (Err) {
+    logAllUnhandledErrors(std::move(Err), outs(), "Error reading file: ");
+    outs().flush();
+    exit(1);
+  }
+}
+
 } // namespace llvm
 
 static void reportError(StringRef Input, StringRef Message) {
@@ -482,9 +490,8 @@ static void dumpCXXData(const ObjectFile *Obj) {
 }
 
 static void dumpArchive(const Archive *Arc) {
-  for (auto &ErrorOrChild : Arc->children()) {
-    error(ErrorOrChild.getError());
-    const Archive::Child &ArcC = *ErrorOrChild;
+  Error Err;
+  for (auto &ArcC : Arc->children(Err)) {
     Expected<std::unique_ptr<Binary>> ChildOrErr = ArcC.getAsBinary();
     if (!ChildOrErr) {
       // Ignore non-object files.
@@ -504,6 +511,7 @@ static void dumpArchive(const Archive *Arc) {
     else
       reportError(Arc->getFileName(), cxxdump_error::unrecognized_file_format);
   }
+  error(std::move(Err));
 }
 
 static void dumpInput(StringRef File) {