Issue #9246: On POSIX, os.getcwd() now supports paths longer than 1025 bytes

Patch written by William Orr.

Misc/NEWS

@@ -34,6 +34,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #9246: On POSIX, os.getcwd() now supports paths longer than 1025 bytes.
+  Patch written by William Orr.
+
 - Issue #23008: Fixed resolving attributes with boolean value is False in pydoc.
 
 - Fix asyncio issue 235: LifoQueue and PriorityQueue's put didn't

Modules/posixmodule.c

@@ -3418,12 +3418,15 @@ posix_lchown(PyObject *self, PyObject *args)
 static PyObject *
 posix_getcwd(int use_bytes)
 {
-    char buf[1026];
-    char *res;
+    char *buf, *tmpbuf;
+    char *cwd;
+    const size_t chunk = 1024;
+    size_t buflen = 0;
+    PyObject *obj;
 
 #ifdef MS_WINDOWS
     if (!use_bytes) {
-        wchar_t wbuf[1026];
+        wchar_t wbuf[MAXPATHLEN];
         wchar_t *wbuf2 = wbuf;
         PyObject *resobj;
         DWORD len;
@@ -3457,14 +3460,31 @@ posix_getcwd(int use_bytes)
         return NULL;
 #endif
 
+    buf = cwd = NULL;
     Py_BEGIN_ALLOW_THREADS
-    res = getcwd(buf, sizeof buf);
+    do {
+        buflen += chunk;
+        tmpbuf = PyMem_RawRealloc(buf, buflen);
+        if (tmpbuf == NULL)
+            break;
+
+        buf = tmpbuf;
+        cwd = getcwd(buf, buflen);
+    } while (cwd == NULL && errno == ERANGE);
     Py_END_ALLOW_THREADS
-    if (res == NULL)
+
+    if (cwd == NULL) {
+        PyMem_RawFree(buf);
         return posix_error();
+    }
+
     if (use_bytes)
-        return PyBytes_FromStringAndSize(buf, strlen(buf));
-    return PyUnicode_DecodeFSDefault(buf);
+        obj = PyBytes_FromStringAndSize(buf, strlen(buf));
+    else
+        obj = PyUnicode_DecodeFSDefault(buf);
+    PyMem_RawFree(buf);
+
+    return obj;
 }
 
 PyDoc_STRVAR(posix_getcwd__doc__,