commit bab4fe320ad2e24c1084fd57d2059ef342688aa9
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Mon Feb 19 23:46:47 2018 -0800
committer Benjamin Peterson <benjamin@python.org> Mon Feb 19 23:46:47 2018 -0800
tree 72e1c61760d3fb4392d56baa8ef5caafbc3b7534
parent a3d6c1b23b8a49b5003fdbd115d3598fe3d4c4bf

closes bpo-32859: Don't retry dup3() if it is not available at runtime (GH-5708)

os.dup2() tests for dup3() system call availability at runtime,
but doesn't remember the result across calls, repeating
the test on each call with inheritable=False.

Since the caller of os.dup2() is expected to hold the GIL,
fix this by making the variable holding the test result static.
(cherry picked from commit b3caf388a0418f6c031e4dbdcc0c1ce7e5cc36bd)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>

Modules/posixmodule.c

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 7304fee..eff74df 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8016,7 +8016,7 @@
 #if defined(HAVE_DUP3) && \
     !(defined(HAVE_FCNTL_H) && defined(F_DUP2FD_CLOEXEC))
     /* dup3() is available on Linux 2.6.27+ and glibc 2.9 */
-    int dup3_works = -1;
+    static int dup3_works = -1;
 #endif
 
     if (fd < 0 || fd2 < 0) {