Fix io.close().

Reported by farmboy0.

src/lib_io.c

@@ -58,12 +58,12 @@ static IOFileUD *io_tofile(lua_State *L)
   return iof;
 }
 
-static FILE *io_stdfile(lua_State *L, ptrdiff_t id)
+static IOFileUD *io_stdfile(lua_State *L, ptrdiff_t id)
 {
   IOFileUD *iof = IOSTDF_IOF(L, id);
   if (iof->fp == NULL)
     lj_err_caller(L, LJ_ERR_IOSTDCL);
-  return iof->fp;
+  return iof;
 }
 
 static IOFileUD *io_file_new(lua_State *L)
@@ -187,8 +187,9 @@ static int io_file_readlen(lua_State *L, FILE *fp, MSize m)
   }
 }
 
-static int io_file_read(lua_State *L, FILE *fp, int start)
+static int io_file_read(lua_State *L, IOFileUD *iof, int start)
 {
+  FILE *fp = iof->fp;
   int ok, n, nargs = (int)(L->top - L->base) - start;
   clearerr(fp);
   if (nargs == 0) {
@@ -225,8 +226,9 @@ static int io_file_read(lua_State *L, FILE *fp, int start)
   return n - start;
 }
 
-static int io_file_write(lua_State *L, FILE *fp, int start)
+static int io_file_write(lua_State *L, IOFileUD *iof, int start)
 {
+  FILE *fp = iof->fp;
   cTValue *tv;
   int status = 1;
   for (tv = L->base+start; tv < L->top; tv++) {
@@ -266,7 +268,7 @@ static int io_file_iter(lua_State *L)
     memcpy(L->top, &fn->c.upvalue[1], n*sizeof(TValue));
     L->top += n;
   }
-  n = io_file_read(L, iof->fp, 0);
+  n = io_file_read(L, iof, 0);
   if (ferror(iof->fp))
     lj_err_callermsg(L, strVdata(L->top-2));
   if (tvisnil(L->base) && (iof->type & IOFILE_FLAG_CLOSE)) {
@@ -292,18 +294,18 @@ static int io_file_lines(lua_State *L)
 LJLIB_CF(io_method_close)
 {
   IOFileUD *iof = L->base < L->top ? io_tofile(L) :
-		  IOSTDF_IOF(L, GCROOT_IO_OUTPUT);
+		  io_stdfile(L, GCROOT_IO_OUTPUT);
   return io_file_close(L, iof);
 }
 
 LJLIB_CF(io_method_read)
 {
-  return io_file_read(L, io_tofile(L)->fp, 1);
+  return io_file_read(L, io_tofile(L), 1);
 }
 
 LJLIB_CF(io_method_write)		LJLIB_REC(io_write 0)
 {
-  return io_file_write(L, io_tofile(L)->fp, 1);
+  return io_file_write(L, io_tofile(L), 1);
 }
 
 LJLIB_CF(io_method_flush)		LJLIB_REC(io_flush 0)
@@ -457,7 +459,7 @@ LJLIB_CF(io_write)		LJLIB_REC(io_write GCROOT_IO_OUTPUT)
 
 LJLIB_CF(io_flush)		LJLIB_REC(io_flush GCROOT_IO_OUTPUT)
 {
-  return luaL_fileresult(L, fflush(io_stdfile(L, GCROOT_IO_OUTPUT)) == 0, NULL);
+  return luaL_fileresult(L, fflush(io_stdfile(L, GCROOT_IO_OUTPUT)->fp) == 0, NULL);
 }
 
 static int io_std_getset(lua_State *L, ptrdiff_t id, const char *mode)