[Python-checkins] closes bpo-36161: Use thread-safe ttyname_r instead of ttyname. (GH-14868)

[Benjamin Peterson]

https://github.com/python/cpython/commit/594e2edfb5e0d24e03469d035d8f39ff29a64d99
commit: 594e2edfb5e0d24e03469d035d8f39ff29a64d99
branch: master
author: Antonio Gutierrez <chibby0ne at gmail.com>
committer: Benjamin Peterson <benjamin at python.org>
date: 2019-10-08T19:19:48-07:00
summary:

closes bpo-36161: Use thread-safe ttyname_r instead of ttyname. (GH-14868)

Signed-off-by: Antonio Gutierrez <chibby0ne at gmail.com>

files:
A Misc/NEWS.d/next/Library/2019-07-20-01-17-43.bpo-36161.Fzf-f9.rst
M Modules/posixmodule.c

diff --git a/Misc/NEWS.d/next/Library/2019-07-20-01-17-43.bpo-36161.Fzf-f9.rst b/Misc/NEWS.d/next/Library/2019-07-20-01-17-43.bpo-36161.Fzf-f9.rst
new file mode 100644
index 0000000000000..b31496c701744
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-07-20-01-17-43.bpo-36161.Fzf-f9.rst
@@ -0,0 +1 @@
+In :mod:`posix`, use ``ttyname_r`` instead of ``ttyname`` for thread safety.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 5664027b2d3a3..aeb0e9ddb1953 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -2774,13 +2774,24 @@ static PyObject *
 os_ttyname_impl(PyObject *module, int fd)
 /*[clinic end generated code: output=c424d2e9d1cd636a input=9ff5a58b08115c55]*/
 {
-    char *ret;
 
-    ret = ttyname(fd);
-    if (ret == NULL) {
+    long size = sysconf(_SC_TTY_NAME_MAX);
+    if (size == -1) {
+        return posix_error();
+    }
+    char *buffer = (char *)PyMem_RawMalloc(size);
+    if (buffer == NULL) {
+        return PyErr_NoMemory();
+    }
+    int ret = ttyname_r(fd, buffer, size);
+    if (ret != 0) {
+        PyMem_RawFree(buffer);
+        errno = ret;
         return posix_error();
     }
-    return PyUnicode_DecodeFSDefault(ret);
+    PyObject *res = PyUnicode_DecodeFSDefault(buffer);
+    PyMem_RawFree(buffer);
+    return res;
 }
 #endif