bpo-24658: os.read() reuses _PY_READ_MAX (GH-10657)

miss-islington · vstinner · web-flow · commit 0c15e508baec · 2018-11-22T06:25:25.000-08:00
os_read_impl() now also truncates the size to _PY_READ_MAX on macOS, to avoid to allocate a larger buffer even if _Py_read() is limited to _PY_READ_MAX bytes (ex: INT_MAX on macOS). (cherry picked from commit 9a0d7a7) Co-authored-by: Victor Stinner <vstinner@redhat.com>
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
@@ -7912,11 +7912,7 @@ os_read_impl(PyObject *module, int fd, Py_ssize_t length)
         return posix_error();
     }
 
-#ifdef MS_WINDOWS
-    /* On Windows, the count parameter of read() is an int */
-    if (length > INT_MAX)
-        length = INT_MAX;
-#endif
+    length = Py_MIN(length, _PY_READ_MAX);
 
     buffer = PyBytes_FromStringAndSize((char *)NULL, length);
     if (buffer == NULL)
