* Use `secure_getenv` instead of

  `getenv` to obtain the value of critical

  environment variables. `secure_getenv`

  environment is not trusted.

  Critical environment variables are debugging flags,

  automatically generated names, e.g., derived from a sequential

  counter. Files with externally provided names could be picked

  up in unexpected contexts, and crafted names could actually

  *directory traversal*).

  Removing a directory tree in a completely safe manner is