[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, 15 insertions, 4 deletions

diff --git a/llvm/tools/llvm-readobj/llvm-readobj.cpp b/llvm/tools/llvm-readobj/llvm-readobj.cpp
index ad97dea2d02..c293919fd95 100644
--- a/llvm/tools/llvm-readobj/llvm-readobj.cpp
+++ b/llvm/tools/llvm-readobj/llvm-readobj.cpp
@@ -295,6 +295,17 @@ static void reportError(StringRef Input, StringRef Message) {
   reportError(Twine(Input) + ": " + Message);
 }
 
+static void reportError(StringRef Input, Error Err) {
+  if (Input == "-")
+    Input = "<stdin>";
+  std::string ErrMsg;
+  {
+    raw_string_ostream ErrStream(ErrMsg);
+    logAllUnhandledErrors(std::move(Err), ErrStream, Input + ": ");
+  }
+  reportError(ErrMsg);
+}
+
 static bool isMipsArch(unsigned Arch) {
   switch (Arch) {
   case llvm::Triple::mips:
@@ -424,10 +435,8 @@ static void dumpObject(const ObjectFile *Obj) {
 
 /// @brief Dumps each object file in \a Arc;
 static void dumpArchive(const Archive *Arc) {
-  for (auto &ErrorOrChild : Arc->children()) {
-    if (std::error_code EC = ErrorOrChild.getError())
-      reportError(Arc->getFileName(), EC.message());
-    const auto &Child = *ErrorOrChild;
+  Error Err;
+  for (auto &Child : Arc->children(Err)) {
     Expected<std::unique_ptr<Binary>> ChildOrErr = Child.getAsBinary();
     if (!ChildOrErr) {
       if (auto E = isNotObjectErrorInvalidFileType(ChildOrErr.takeError())) {
@@ -444,6 +453,8 @@ static void dumpArchive(const Archive *Arc) {
     else
       reportError(Arc->getFileName(), readobj_error::unrecognized_file_format);
   }
+  if (Err)
+    reportError(Arc->getFileName(), std::move(Err));
 }
 
 /// @brief Dumps each object file in \a MachO Universal Binary;