obj2yaml: Improve error reporting

[sbc100]

Summary

Previously only the error codes were reported which
meant that useful information about malformed imputs
was not shown.

[sbc100]

• update tests

[davide]

This looks fine. Are there other places in obj2yaml that could take advantage of the new Error scheme? If so, I'd convert them all together.

[sbc100]

Yes, I think there is lager change to made here. For example ELFObjectFile from libObject still doesn't report Error's. However I think this change stands alone as a useful fix and we can follewup with others.

test/Object/obj2yaml.test

 
 ELF-X86-64-UNWIND:      - Name:            .eh_frame
 ELF-X86-64-UNWIND-NEXT:   Type:            SHT_X86_64_UNWIND
 ELF-X86-64-UNWIND-NEXT:   Flags:           [ SHF_ALLOC ]
 ELF-X86-64-UNWIND-NEXT:   AddressAlign:    0x0000000000000001
 ELF-X86-64-UNWIND-NEXT:   Content:         ''
 
 RUN: not obj2yaml %t.blah 2>&1 | FileCheck --check-prefix=ENOENT %s
-ENOENT: Error: '{{[Nn]}}o such file or directory'
+ENOENT: Error reading file: {{.*}}.blah: {{[Nn]}}o such file or directory

test/ObjectYAML/wasm/header_invalid_version.yaml

 # RUN: yaml2obj %s | not obj2yaml 2>&1 | FileCheck %s
 --- !WASM
 FileHeader:
   Version:         0x00000002
 ...
-# CHECK: Error: 'Invalid data was encountered while parsing the file'
+# CHECK: Error reading file: <stdin>: Bad version number

test/tools/obj2yaml/invalid_input_file.test

+# RUN: not obj2yaml  %p/path/does/not/exist 2>&1 | FileCheck %s
+
+# Don't check the OS-dependent message "No such file or directory".
+# CHECK: Error reading file: {{.*}}/path/does/not/exist: {{.*}}

tools/obj2yaml/obj2yaml.cpp

static std::error_code dumpObject(const ObjectFile &Obj) {
   if (Obj.isELF())
     return elf2yaml(outs(), Obj);
   if (Obj.isWasm())
     return wasm2yaml(outs(), cast<WasmObjectFile>(Obj));
 
   return obj2yaml_error::unsupported_obj_file_format;
 }
 
-static std::error_code dumpInput(StringRef File) {
+static Error dumpInput(StringRef File) {
   Expected<OwningBinary<Binary>> BinaryOrErr = createBinary(File);
   if (!BinaryOrErr)
-    return errorToErrorCode(BinaryOrErr.takeError());
+    return BinaryOrErr.takeError();
 
   Binary &Binary = *BinaryOrErr.get().getBinary();
   // Universal MachO is not a subclass of ObjectFile, so it needs to be handled
   // here with the other binary types.
   if (Binary.isMachO() || Binary.isMachOUniversalBinary())
-    return macho2yaml(outs(), Binary);
+    return errorCodeToError(macho2yaml(outs(), Binary));
   // TODO: If this is an archive, then burst it and dump each entry
   if (ObjectFile *Obj = dyn_cast<ObjectFile>(&Binary))
-    return dumpObject(*Obj);
+    return errorCodeToError(dumpObject(*Obj));
 
-  return obj2yaml_error::unrecognized_file_format;
+  return Error::success();
+}
+
+static void reportError(StringRef Input, Error Err) {
+  if (Input == "-")
+    Input = "<stdin>";
+  std::string ErrMsg;
+  raw_string_ostream OS(ErrMsg);
+  logAllUnhandledErrors(std::move(Err), OS, "");
+  OS.flush();
+  errs() << "Error reading file: " << Input << ": " << ErrMsg;
+  errs().flush();
 }
 
 cl::opt<std::string> InputFilename(cl::Positional, cl::desc("<input file>"),
                                    cl::init("-"));
 
 int main(int argc, char *argv[]) {
   cl::ParseCommandLineOptions(argc, argv);
   sys::PrintStackTraceOnErrorSignal(argv[0]);
   PrettyStackTraceProgram X(argc, argv);
   llvm_shutdown_obj Y; // Call llvm_shutdown() on exit.
 
-  if (std::error_code EC = dumpInput(InputFilename)) {
-    errs() << "Error: '" << EC.message() << "'\n";
+  if (Error Err = dumpInput(InputFilename)) {
+    reportError(InputFilename, std::move(Err));
     return 1;
   }
 
   return 0;
 }