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/clmodule.c b/Modules/clmodule.c
index ef3d77a..70e8f8e 100644
--- a/Modules/clmodule.c
+++ b/Modules/clmodule.c
@@ -135,8 +135,7 @@ cl_CompressImage(PyObject *self, PyObject *args)
 	}
 
 	if (compressedBufferSize < frameBufferSize)
-		if (_PyString_Resize(&compressedBuffer, compressedBufferSize))
-			return NULL;
+		_PyString_Resize(&compressedBuffer, compressedBufferSize);
 
 	return compressedBuffer;
 }