Test program to reproduce the bug

gentoo-llvm-repro.cpp (text/x-c++src), 330 bytes, created by Magnus Lång on 2018-11-26 23:46:32 UTC

#include <llvm/Support/CommandLine.h>

#include <iostream>

llvm::cl::opt<std::string>
cl_input(llvm::cl::desc("<actual input file>"),
         llvm::cl::Positional,
         llvm::cl::init("-"));

int main(int argc, char *argv[]){
  llvm::cl::ParseCommandLineOptions(argc, argv);

  std::cout << cl_input << "\n";

  return 0;
}