Repair widespread misuse of _PyString_Resize. Since it's clear people

don't understand how this function works, also beefed up the docs.  The
most common usage error is of this form (often spread out across gotos):

	if (_PyString_Resize(&s, n) < 0) {
		Py_DECREF(s);
		s = NULL;
		goto outtahere;
	}

The error is that if _PyString_Resize runs out of memory, it automatically
decrefs the input string object s (which also deallocates it, since its
refcount must be 1 upon entry), and sets s to NULL.  So if the "if"
branch ever triggers, it's an error to call Py_DECREF(s):  s is already
NULL!  A correct way to write the above is the simpler (and intended)

	if (_PyString_Resize(&s, n) < 0)
		goto outtahere;

Bugfix candidate.

1 files changed, 1 insertions, 2 deletions

diff --git a/Modules/linuxaudiodev.c b/Modules/linuxaudiodev.c
index fa2e441..7d4abc9 100644
--- a/Modules/linuxaudiodev.c
+++ b/Modules/linuxaudiodev.c
@@ -158,8 +158,7 @@ lad_read(lad_t *self, PyObject *args)
         return NULL;
     }
     self->x_icount += count;
-    if (_PyString_Resize(&rv, count) == -1)
-	return NULL;
+    _PyString_Resize(&rv, count);
     return rv;
 }