posix_putenv(): Constrain memory leakage when setting the same

        environment variable repeatedly.  I posted this to the list
        some time ago, but only now got around to asking g--d- what he
        thought about it.

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 947e1691eb6a66034a27482a2dc36efce81aec0b..61c9a21d41b04049734ae87c4847d779bc4f55ea 100644 (file)
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -2787,6 +2787,10 @@ Change or add an environment variable.";
 int putenv( const char *str );
 #endif
 
+/* Save putenv() parameters as values here, so we can collect them when they
+ * get re-set with another call for the same key. */
+static PyObject *posix_putenv_garbage;
+
 static PyObject * 
 posix_putenv(self, args)
        PyObject *self;
@@ -2794,6 +2798,7 @@ posix_putenv(self, args)
 {
         char *s1, *s2;
         char *new;
+       PyObject *newstr;
 
        if (!PyArg_ParseTuple(args, "ss", &s1, &s2))
                return NULL;
@@ -2821,14 +2826,28 @@ posix_putenv(self, args)
     } else {
 #endif
 
-       /* XXX This leaks memory -- not easy to fix :-( */
-       if ((new = malloc(strlen(s1) + strlen(s2) + 2)) == NULL)
-                return PyErr_NoMemory();
+       /* XXX This can leak memory -- not easy to fix :-( */
+       newstr = PyString_FromStringAndSize(NULL, strlen(s1) + strlen(s2) + 2);
+       if (newstr == NULL)
+               return PyErr_NoMemory();
+       new = PyString_AS_STRING(newstr);
        (void) sprintf(new, "%s=%s", s1, s2);
        if (putenv(new)) {
                 posix_error();
                 return NULL;
        }
+       /* Install the first arg and newstr in posix_putenv_garbage;
+        * this will cause previous value to be collected.  This has to
+        * happen after the real putenv() call because the old value
+        * was still accessible until then. */
+       if (PyDict_SetItem(posix_putenv_garbage,
+                          PyTuple_GET_ITEM(args, 0), newstr)) {
+               /* really not much we can do; just leak */
+               PyErr_Clear();
+       }
+       else {
+               Py_DECREF(newstr);
+       }
 
 #if defined(PYOS_OS2)
     }
@@ -3500,4 +3519,6 @@ INITFUNC()
                 return;
 
        PyDict_SetItemString(d, "error", PyExc_OSError);
+
+       posix_putenv_garbage = PyDict_New();
 }