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GNU Guile < = 2.0.12 Thread-unsafe umask modification

Posted on 30 November -0001

<HTML><HEAD><TITLE>GNU Guile <= 2.0.12 Thread-unsafe umask modification</TITLE><META http-equiv="Content-Type" content="text/html; charset=utf-8"></HEAD><BODY>Hello!

When the optional ‘mode' argument to the ‘mkdir' procedure is omitted,
umask(2) is used to find out what the current mask is and to compute the
mode argument to mkdir(2):

--8<---------------cut here---------------start------------->8---
  if (SCM_UNBNDP (mode))
    {
      mask = umask (0);
      umask (mask);
      STRING_SYSCALL (path, c_path, rv = mkdir (c_path, 0777 ^ mask));
    }
--8<---------------cut here---------------end--------------->8---

The problem is that this changes the process' umask globally for a short
duration, during which other threads will get 0 as the mask…

Furthermore, AFAICS, the above logic is redundant with what the kernel
does anyway.  That is, in a single-threaded program,

  mask = umask (0);
  umask (mask);
  mkdir (file, 0777 ^ mask);

is equivalent to:

  mkdir (file, 0777);

Am I right that we should just remove these two ‘umask' calls?

Ludo'.

PS: This code has been there since 1996 or earlier.
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