[Python-checkins] bpo-32849: Fix is_valid_fd() on FreeBSD (GH-12852)

Wed Apr 17 12:09:26 EDT 2019

https://github.com/python/cpython/commit/3092d6b2630e4d2bd200fbc3231c27a7cba4d6b2
commit: 3092d6b2630e4d2bd200fbc3231c27a7cba4d6b2
branch: master
author: Victor Stinner <vstinner at redhat.com>
committer: GitHub <noreply at github.com>
date: 2019年04月17日T18:09:12+02:00
summary:
bpo-32849: Fix is_valid_fd() on FreeBSD (GH-12852)
Fix Python Initialization code on FreeBSD to detect properly when
stdin file descriptor (fd 0) is invalid.
On FreeBSD, fstat() must be used to check if stdin (fd 0) is valid.
dup(0) doesn't fail if stdin is invalid in some cases.
files:
A Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-56-12.bpo-32849.aeSg-D.rst
M Python/pylifecycle.c

diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-56-12.bpo-32849.aeSg-D.rst b/Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-56-12.bpo-32849.aeSg-D.rst
new file mode 100644
index 000000000000..6a9a85c4b134
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-56-12.bpo-32849.aeSg-D.rst	
@@ -0,0 +1,2 @@
+Fix Python Initialization code on FreeBSD to detect properly when stdin file
+descriptor (fd 0) is invalid.
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index ad1447256cc6..c7920ef6262d 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -1664,26 +1664,34 @@ initsite(void)
 static int
 is_valid_fd(int fd)
 {
-#ifdef __APPLE__
- /* bpo-30225: On macOS Tiger, when stdout is redirected to a pipe
- and the other side of the pipe is closed, dup(1) succeed, whereas
- fstat(1, &st) fails with EBADF. Prefer fstat() over dup() to detect
- such error. */
- struct stat st;
- return (fstat(fd, &st) == 0);
-#else
- int fd2;
- if (fd < 0)
+/* dup() is faster than fstat(): fstat() can require input/output operations,
+ whereas dup() doesn't. There is a low risk of EMFILE/ENFILE at Python
+ startup. Problem: dup() doesn't check if the file descriptor is valid on
+ some platforms.
+
+ bpo-30225: On macOS Tiger, when stdout is redirected to a pipe and the other
+ side of the pipe is closed, dup(1) succeed, whereas fstat(1, &st) fails with
+ EBADF. FreeBSD has similar issue (bpo-32849).
+
+ Only use dup() on platforms where dup() is enough to detect invalid FD in
+ corner cases: on Linux and Windows (bpo-32849). */
+#if defined(__linux__) || defined(MS_WINDOWS)
+ if (fd < 0) {
 return 0;
+ }
+ int fd2;
+
 _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)
+ if (fd2 >= 0) {
 close(fd2);
+ }
 _Py_END_SUPPRESS_IPH
- return fd2 >= 0;
+
+ return (fd2 >= 0);
+#else
+ struct stat st;
+ return (fstat(fd, &st) == 0);
 #endif
 }
 
