Trivially parsing clang command line args with clang itself.

args_with_clang.cpp

#include <llvm/Option/ArgList.h>
#include <llvm/Option/Arg.h>
#include <clang/Driver/Options.h>
#include <llvm/Option/OptTable.h>
#include <llvm/Support/raw_ostream.h>

#include <memory>

using namespace llvm;
using namespace llvm::opt;
using namespace clang;
using namespace clang::driver;

int main(int argc, char *argv[]) {
  std::unique_ptr<OptTable> OptTable(driver::createDriverOptTable());
  
  unsigned int MissingArgIndex;
  unsigned int MissingArgCount = 0;
  std::unique_ptr<InputArgList> Args(
    OptTable->ParseArgs(
      &argv[1],
      &argv[argc],
      MissingArgIndex,
      MissingArgCount,
      0,
      options::CLOption | options::NoDriverOption));
  
  if (MissingArgCount > 0) {
    errs() << "Argument missing values: " << argv[MissingArgIndex] << " " << MissingArgCount;
    return 100;
  }
  
  for (auto it = Args->filtered_begin(options::OPT_UNKNOWN),
            ie = Args->filtered_end(); it != ie; ++it) {
    errs() << "Unknown argument: " << (*it)->getAsString(*Args) << "\n";
    return 100;
  }
  
  for (Arg *arg : *Args) {
    outs() << arg->getAsString(*Args) << "\n";
  }
  
  return 0;
}