From: Victor Stinner <victor.stinner@gmail.com>
Date: Tue, 29 Sep 2015 11:59:50 +0000 (+0200)
Subject: Issue #18174: Explain why is_valid_fd() uses dup() instead of fstat()
X-Git-Tag: v3.6.0a1~1401
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=449b27179931aa570597556ed4865ac2f1f981c9;p=thirdparty%2FPython%2Fcpython.git

Issue #18174: Explain why is_valid_fd() uses dup() instead of fstat()
---

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 4f5efc963c77..857a543cf546 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -972,6 +972,9 @@ is_valid_fd(int fd)
     if (fd < 0 || !_PyVerify_fd(fd))
         return 0;
     _Py_BEGIN_SUPPRESS_IPH
+    /* Prefer dup() over fstat(). fstat() can require input/output whereas
+       dup() doesn't, there is a low risk of EMFILE/ENFILE at Python
+       startup. */
     fd2 = dup(fd);
     if (fd2 >= 0)
         close(fd2);