[Python-checkins] r51363 - in python/branches/release24-maint: Doc/api/abstract.tex Doc/api/concrete.tex Doc/api/intro.tex Misc/NEWS

[georg.brandl]

Author: georg.brandl
Date: Fri Aug 18 09:25:22 2006
New Revision: 51363

Modified:
   python/branches/release24-maint/Doc/api/abstract.tex
   python/branches/release24-maint/Doc/api/concrete.tex
   python/branches/release24-maint/Doc/api/intro.tex
   python/branches/release24-maint/Misc/NEWS
Log:
Bug #1541682: Fix example in the "Refcount details" API docs.
Additionally, remove a faulty example showing PySequence_SetItem applied
to a newly created list object and add notes that this isn't a good idea.
 (backport)

Modified: python/branches/release24-maint/Doc/api/abstract.tex
==============================================================================
--- python/branches/release24-maint/Doc/api/abstract.tex	(original)
+++ python/branches/release24-maint/Doc/api/abstract.tex	Fri Aug 18 09:25:22 2006
@@ -5,6 +5,10 @@
 numerical types, or all sequence types).  When used on object types
 for which they do not apply, they will raise a Python exception.
 
+It is not possible to use these functions on objects that are not properly
+initialized, such a list object that has been created by
+\cfunction{PyList_New()}, but whose items have not been set to some
+non-\code{NULL} value yet.
 
 \section{Object Protocol \label{object}}
 

Modified: python/branches/release24-maint/Doc/api/concrete.tex
==============================================================================
--- python/branches/release24-maint/Doc/api/concrete.tex	(original)
+++ python/branches/release24-maint/Doc/api/concrete.tex	Fri Aug 18 09:25:22 2006
@@ -1766,6 +1766,11 @@
 \begin{cfuncdesc}{PyObject*}{PyList_New}{int len}
   Return a new list of length \var{len} on success, or \NULL{} on
   failure.
+  \note{If \var{length} is greater than zero, the returned list object's
+        items are set to \code{NULL}.  Thus you cannot use abstract
+        API functions such as \cfunction{PySequence_SetItem()} on it
+        or expose it to Python code before setting all items to a
+        real object with \cfunction{PyList_SetItem()}.}
 \end{cfuncdesc}
 
 \begin{cfuncdesc}{int}{PyList_Size}{PyObject *list}

Modified: python/branches/release24-maint/Doc/api/intro.tex
==============================================================================
--- python/branches/release24-maint/Doc/api/intro.tex	(original)
+++ python/branches/release24-maint/Doc/api/intro.tex	Fri Aug 18 09:25:22 2006
@@ -225,25 +225,10 @@
 \cfunction{PyTuple_SetItem()} for tuples that you are creating
 yourself.
 
-Equivalent code for populating a list can be written using 
-\cfunction{PyList_New()} and \cfunction{PyList_SetItem()}.  Such code
-can also use \cfunction{PySequence_SetItem()}; this illustrates the
-difference between the two (the extra \cfunction{Py_DECREF()} calls):
+Equivalent code for populating a list can be written using
+\cfunction{PyList_New()} and \cfunction{PyList_SetItem()}.
 
-\begin{verbatim}
-PyObject *l, *x;
-
-l = PyList_New(3);
-x = PyInt_FromLong(1L);
-PySequence_SetItem(l, 0, x); Py_DECREF(x);
-x = PyInt_FromLong(2L);
-PySequence_SetItem(l, 1, x); Py_DECREF(x);
-x = PyString_FromString("three");
-PySequence_SetItem(l, 2, x); Py_DECREF(x);
-\end{verbatim}
-
-You might find it strange that the ``recommended'' approach takes more
-code.  However, in practice, you will rarely use these ways of
+However, in practice, you will rarely use these ways of
 creating and populating a tuple or list.  There's a generic function,
 \cfunction{Py_BuildValue()}, that can create most common objects from
 C values, directed by a \dfn{format string}.  For example, the
@@ -251,10 +236,10 @@
 also takes care of the error checking):
 
 \begin{verbatim}
-PyObject *t, *l;
+PyObject *tuple, *list;
 
-t = Py_BuildValue("(iis)", 1, 2, "three");
-l = Py_BuildValue("[iis]", 1, 2, "three");
+tuple = Py_BuildValue("(iis)", 1, 2, "three");
+list = Py_BuildValue("[iis]", 1, 2, "three");
 \end{verbatim}
 
 It is much more common to use \cfunction{PyObject_SetItem()} and
@@ -276,8 +261,12 @@
     if (n < 0)
         return -1;
     for (i = 0; i < n; i++) {
-        if (PyObject_SetItem(target, i, item) < 0)
+        PyObject *index = PyInt_FromLong(i);
+        if (!index)
+            return -1;
+        if (PyObject_SetItem(target, index, item) < 0)
             return -1;
+        Py_DECREF(index);
     }
     return 0;
 }

Modified: python/branches/release24-maint/Misc/NEWS
==============================================================================
--- python/branches/release24-maint/Misc/NEWS	(original)
+++ python/branches/release24-maint/Misc/NEWS	Fri Aug 18 09:25:22 2006
@@ -166,6 +166,10 @@
 Documentation
 -------------
 
+- Bug #1541682: Fix example in the "Refcount details" API docs.
+  Additionally, remove a faulty example showing PySequence_SetItem applied
+  to a newly created list object and add notes that this isn't a good idea.
+
 - Clarified documentation for tp_as_buffer->bf_getcharbuffer.
 
 - Bug #1337990: clarified that ``doctest`` does not support examples