Would the _WIN32 version also need such a fix?

I've fixed @peterschrammel's lint errors. Unfortunately I don't have a Windows environment set up to implement and test this behaviour on Windows. I only use this fix in regression tests in the security scanner repo though so any issues will be quickly apparent and won't affect core CBMC.

I believe @kroening has a Windows environment (and there would be one available via AppVeyor).

Does @kroening want to test the following code to see if it can delete a folder containing a sub-folder and some files? If this is going to take much more of my time though I'm probably just going to close this issue and give up. Shame you can't get an improvement into CBMC without having to fix other broken code around it. Makes things take so long that really shouldn't.

  struct _finddata_t info;
  intptr_t hFile=_findfirst(pattern.c_str(), &info);
  if(hFile!=-1)
  {
    do {
      std::string sub_path=path+"\\"+info.name;
      if(info.attrib==_A_SUBDIR)
        delete_directory(sub_path);
      else
        unlink(sub_path);
    } while(_findnext(hFile, &info)==0)
    _findclose(hFile);
  }

Did the previous code even work on Windows? unlink seems to be called with a path relative to the passed folder.

I suggest to create a unit test for this in the /unit folder. So, we know at least if it works/worked/will-work-soon on all platforms.

Code written and tested by @smowton for Windows has been added.

Thanks @NathanJPhillips and @smowton!