bpo-38110: Use fdwalk for os.closerange() when available. (GH-15224)

Use fdwalk() on platforms that support it to implement os.closerange().

Misc/NEWS.d/next/Library/2019-09-11-14-49-20.bpo-38110.A19Y-q.rst

+The os.closewalk() implementation now uses the libc fdwalk() API on
+platforms where it is available.

Modules/posixmodule.c

@@ -8422,6 +8422,21 @@ os_close_impl(PyObject *module, int fd)
 }
 
 
+#ifdef HAVE_FDWALK
+static int
+_fdwalk_close_func(void *lohi, int fd)
+{
+    int lo = ((int *)lohi)[0];
+    int hi = ((int *)lohi)[1];
+
+    if (fd >= hi)
+        return 1;
+    else if (fd >= lo)
+        close(fd);
+    return 0;
+}
+#endif /* HAVE_FDWALK */
+
 /*[clinic input]
 os.closerange
 
@@ -8436,11 +8451,21 @@ static PyObject *
 os_closerange_impl(PyObject *module, int fd_low, int fd_high)
 /*[clinic end generated code: output=0ce5c20fcda681c2 input=5855a3d053ebd4ec]*/
 {
+#ifdef HAVE_FDWALK
+    int lohi[2];
+#else
     int i;
+#endif
     Py_BEGIN_ALLOW_THREADS
     _Py_BEGIN_SUPPRESS_IPH
+#ifdef HAVE_FDWALK
+    lohi[0] = Py_MAX(fd_low, 0);
+    lohi[1] = fd_high;
+    fdwalk(_fdwalk_close_func, lohi);
+#else
     for (i = Py_MAX(fd_low, 0); i < fd_high; i++)
         close(i);
+#endif
     _Py_END_SUPPRESS_IPH
     Py_END_ALLOW_THREADS
     Py_RETURN_NONE;

configure

@@ -11500,7 +11500,7 @@ fi
 for ac_func in alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  clock confstr copy_file_range ctermid dup3 execv explicit_bzero explicit_memset \
  faccessat fchmod fchmodat fchown fchownat \
- fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
+ fdwalk fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
  futimens futimes gai_strerror getentropy \
  getgrgid_r getgrnam_r \
  getgrouplist getgroups getlogin getloadavg getpeername getpgid getpid \

configure.ac

@@ -3538,7 +3538,7 @@ fi
 AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  clock confstr copy_file_range ctermid dup3 execv explicit_bzero explicit_memset \
  faccessat fchmod fchmodat fchown fchownat \
- fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
+ fdwalk fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
  futimens futimes gai_strerror getentropy \
  getgrgid_r getgrnam_r \
  getgrouplist getgroups getlogin getloadavg getpeername getpgid getpid \

pyconfig.h.in

@@ -337,6 +337,9 @@
 /* Define to 1 if you have the `fdopendir' function. */
 #undef HAVE_FDOPENDIR
 
+/* Define to 1 if you have the `fdwalk' function. */
+#undef HAVE_FDWALK
+
 /* Define to 1 if you have the `fexecve' function. */
 #undef HAVE_FEXECVE