Writing a program taking LLVM IR file as a Command line argument - c++

Question

I am writing a main.cpp file for testing LLVM IR Command line argument .
I am using llvm version : 6.0.1
#include<iostream>
#include <llvm/Bitcode/BitcodeReader.h>
#include <llvm/Bitcode/BitcodeWriter.h>
#include "llvm/IR/Function.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/raw_ostream.h"
#include <llvm/Support/Error.h>
#include <llvm/IRReader/IRReader.h>
using namespace llvm;
using namespace std;
static cl::opt<string> input(cl::Positional, cl::desc("Bitcode file"), cl::Required);
int main(int argc, char** argv)
{
cl::ParseCommandLineOptions(argc, argv, "LLVM IR to Bytecode \n");
LLVMContext context;
ErrorOr<std::unique_ptr<MemoryBuffer>> mb = MemoryBuffer::getFile(input);
if (error_code ec = mb.getError()) {
errs() << ec.message();
return -1;
}
ErrorOr<std::unique_ptr<Module>> m=parseBitcodeFile(mb->get()->getMemBufferRef(), context);
if (error_code ec = m.getError())
{
errs() << "Error reading bitcode: " << ec.message() << "\n";
return -1;
}
return 0;
}
I got this error :
error: ‘class llvm::Expected >’ has no member named ‘getError’
if (error_code ec = m.getError())
I google many times but I do not found answer any where. Please suggest me some solution.

Answer 1

The above error was due to change in LLVM API over a time. Change module reader functions to return an llvm::Expected <T> []https://reviews.llvm.org/D26562
. This class parallels ErrorOr, but replaces error_code with Error. Since Error cannot be copied, this class replaces getError() with takeError().
So above code changes to :
Expected<std::unique_ptr<Module>> m = parseBitcodeFile(mb->get()->getMemBufferRef(), context);
if (std::error_code ec = errorToErrorCode(m.takeError())) {
errs() << "Error reading bitcode: " << ec.message() << "\n";
return -1;
}