Re: lua bug - loadfile gets stdin confused

[David Manura <dm.gmane@...>]

David Manura <dm.gmane <at> math2.org> writes:
> The following code demonstrates what seems to be a bug in Lua 5.1.2.
> It affects at least Win32.
>
> io.input():close()  -- breaks it
> --io.input(io.open("NUL")) -- unbreaks it
> loadfile("1.lua")  -- does not close file!
>                    --   culprit in lauxlib.c:luaL_loadfile:
>                    --   if (lf.f != stdin) fclose(lf.f);
> collectgarbage()   -- no help
> ...
> os.execute("notepad")  -- pause to allow user to test above

It's more directly seen with this test case:

local f = io.open("1.lua", "w")
f:write("print('test')")
f:close()

io.input():close()  -- breaks it
--local f = io.open("NUL") -- unbreaks it
local f = io.open("1.lua")  -- overwrites C stdin !
dofile() -- prints "test" !
-- culprit is "lf.f = stdin;" in lauxlib.c:luaL_loadfile

Here's a similar example in C:

#include <stdio.h>
int main()
{
  FILE * f;
  int c;

  fclose(stdin);
  f = fopen("in.txt", "r");
  while((c = fgetc(stdin)) != -1) fputc(c, stdout); /* prints in.txt ! */

  return 0;
}