[llvm-objcopy] Return Error from Buffer::allocate(), [ELF]Writer::finalize(), and [ELF]Writer::commit()

Summary:
This patch changes a few methods to return Error instead of manually calling error/reportError to abort. This will make it easier to extract into a library.

Note that error() takes just a string (this patch also adds an overload that takes an Error), while reportError() takes string + [error/code]. To help unify things, use FileError to associate a given filename with an error. Note that this takes some special care (for now), e.g. calling reportError(FileName, <something that could be FileError>) will duplicate the filename. The goal is to eventually remove reportError() and have every error associated with a file to be a FileError, and just one error handling block at the tool level.

This change was suggested in D56806. I took it a little further than suggested, but completely fixing llvm-objcopy will take a couple more patches. If this approach looks good, I'll commit this and apply similar patche(s) for the rest.

This change is NFC in terms of non-error related code, although the error message changes in one context.

Reviewers: alexshap, jhenderson, jakehehrlich, mstorsjo, espindola

Reviewed By: alexshap, jhenderson

Subscribers: llvm-commits, emaste, arichardson

Differential Revision: https://reviews.llvm.org/D56930

llvm-svn: 351896

1 files changed, 14 insertions, 6 deletions

diff --git a/llvm/tools/llvm-objcopy/Buffer.cpp b/llvm/tools/llvm-objcopy/Buffer.cpp
index 2da03dee1af..1789097f276 100644
--- a/llvm/tools/llvm-objcopy/Buffer.cpp
+++ b/llvm/tools/llvm-objcopy/Buffer.cpp
@@ -17,23 +17,31 @@ namespace objcopy {
 
 Buffer::~Buffer() {}
 
-void FileBuffer::allocate(size_t Size) {
+Error FileBuffer::allocate(size_t Size) {
   Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
       FileOutputBuffer::create(getName(), Size, FileOutputBuffer::F_executable);
-  handleAllErrors(BufferOrErr.takeError(), [this](const ErrorInfoBase &E) {
-    error("failed to open " + getName() + ": " + E.message());
-  });
+  // FileOutputBuffer::create() returns an Error that is just a wrapper around
+  // std::error_code. Wrap it in FileError to include the actual filename.
+  if (!BufferOrErr)
+    return createFileError(getName(), BufferOrErr.takeError());
   Buf = std::move(*BufferOrErr);
+  return Error::success();
 }
 
-Error FileBuffer::commit() { return Buf->commit(); }
+Error FileBuffer::commit() {
+  Error Err = Buf->commit();
+  // FileOutputBuffer::commit() returns an Error that is just a wrapper around
+  // std::error_code. Wrap it in FileError to include the actual filename.
+  return Err ? createFileError(getName(), std::move(Err)) : std::move(Err);
+}
 
 uint8_t *FileBuffer::getBufferStart() {
   return reinterpret_cast<uint8_t *>(Buf->getBufferStart());
 }
 
-void MemBuffer::allocate(size_t Size) {
+Error MemBuffer::allocate(size_t Size) {
   Buf = WritableMemoryBuffer::getNewMemBuffer(Size, getName());
+  return Error::success();
 }
 
 Error MemBuffer::commit() { return Error::success(); }