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Re: [Libvir] [PATCH] python/libvir.c (VIR_PY_NONE): New macro, to encapsulate a common two-statement sequence. Handle PyTuple_New's malloc failure. Use VIR_PY_NONE.



Thanks for the review, Rich.

Seeing that messed-up Subject: line, I realized that
I sent a patch produced by "git-format-patch",
forgetting that the ancient version of mailman behind
this list would remove important parts of it.

For the record, here's what I really sent:
(with the "From " line escaped)

From: Jim Meyering <jim meyering net>
To: "Daniel P. Berrange" <berrange redhat com>
Cc: Libvirt <libvir-list redhat com>
Subject: Re: [Libvir] handle PyTuple_New's malloc failure
In-Reply-To: <20080117155200 GC21549 redhat com> (Daniel P. Berrange's message
	of "Thu, 17 Jan 2008 15:52:00 +0000")
References: <87zlv4larm fsf rho meyering net>
	<20080117155200 GC21549 redhat com>
Date: Thu, 17 Jan 2008 19:59:07 +0100
Message-ID: <87y7aojn2c fsf rho meyering net>

"Daniel P. Berrange" <berrange redhat com> wrote:
> On Thu, Jan 17, 2008 at 04:41:49PM +0100, Jim Meyering wrote:
>> python/libvir.c calls PyTuple_New, but doesn't handle the possibility
>> of a NULL return value.  Subsequent use of the result pointer in e.g.,
>> PyTuple_SetItem, would dereference it.
>>
>> This fixes most of them, but leaves the ones in
>> virConnectCredCallbackWrapper untouched.  Fixing them
>> properly is not as easy, and IMHO will require actual testing.
>>
>> In this patch, I combined each new test like this
>>
>>   ((info = PyTuple_New(8)) == NULL)
>>
>> with the preceding "if (c_retval < 0)", since the bodies would be the same.
>>
>> Duplicating that 2-line body might look more readable,
>> depending on which side of the bed you get up on...
>> I can go either way.

> Might be useful to have a macro to combine the Py_INCREF and return
> (Py_None) in one convenient blob.  return VIR_PY_NONE();

Good idea.  That makes the patch a lot bigger, but makes the
resulting code more readable, too.

> I think it'd be nicer to keep the PyTuple_new bit separate as it is
> now, because in some APIs there can be other code between the existing
> c_retval < 0 check, and the point at which we create the Tuple.
>
> eg, the libvirt_virDomainGetSchedulerParameters  method in the
> patch I'm attaching which implements a number of missing APIs
> NB, this patch is not tested yet, so not intended to be applied

Makes sense.  And with VIR_PY_NONE, the duplication isn't a problem.
New patch below.

> I curious as to why we ever return(NULL) here rather than Py_None. I'm
> not sure of the python runtime / C binding contract - but returning an
> actual NULL seems odd.

Me too.

Here's the combined patch.
Considering the number of uses of VIR_PY_NONE this introduces,
I'll have to do the right thing and split it into two: one that
adds VIR_PY_NONE, and another that fixes the NULL-deref bugs.


> From 55bafd1bdaf6dde1bd019397f569d397fea366a6 Mon Sep 17 00:00:00 2001
> From: Jim Meyering <meyering redhat com>
> Date: Thu, 17 Jan 2008 16:40:17 +0100
> Subject: [PATCH] python/libvir.c (VIR_PY_NONE): New macro, to encapsulate a common
 two-statement sequence.
 Handle PyTuple_New's malloc failure.
 Use VIR_PY_NONE.


Signed-off-by: Jim Meyering <meyering redhat com>
---
 python/libvir.c |  177 +++++++++++++++++++++----------------------------------
 1 files changed, 68 insertions(+), 109 deletions(-)

diff --git a/python/libvir.c b/python/libvir.c
index 3b41dc1..dbf148e 100644
--- a/python/libvir.c
+++ b/python/libvir.c
@@ -31,6 +31,11 @@ PyObject * libvirt_virDomainBlockStats(PyObject *self ATTRIBUTE_UNUSED, PyObject
 PyObject * libvirt_virDomainInterfaceStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args);
 PyObject * libvirt_virNodeGetCellsFreeMemory(PyObject *self ATTRIBUTE_UNUSED, PyObject *args);
 
+/* The two-statement sequence "Py_INCREF(Py_None); return Py_None;"
+   is so common that we encapsulate it here.  Now, each use is simply
+   return VIR_PY_NONE;  */
+#define VIR_PY_NONE (Py_INCREF (Py_None), Py_None)
+
 /************************************************************************
  *									*
  *		Statistics						*
@@ -48,17 +53,16 @@ libvirt_virDomainBlockStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
 
     if (!PyArg_ParseTuple(args, (char *)"Oz:virDomainBlockStats",
         &pyobj_domain,&path))
-	return(NULL);
+        return(NULL);
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
     c_retval = virDomainBlockStats(domain, path, &stats, sizeof(stats));
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
 
-    /* convert to a Python tupple of long objects */
-    info = PyTuple_New(5);
+    /* convert to a Python tuple of long objects */
+    if ((info = PyTuple_New(5)) == NULL)
+        return VIR_PY_NONE;
     PyTuple_SetItem(info, 0, PyLong_FromLongLong(stats.rd_req));
     PyTuple_SetItem(info, 1, PyLong_FromLongLong(stats.rd_bytes));
     PyTuple_SetItem(info, 2, PyLong_FromLongLong(stats.wr_req));
@@ -82,13 +86,12 @@ libvirt_virDomainInterfaceStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
     c_retval = virDomainInterfaceStats(domain, path, &stats, sizeof(stats));
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
 
-    /* convert to a Python tupple of long objects */
-    info = PyTuple_New(8);
+    /* convert to a Python tuple of long objects */
+    if ((info = PyTuple_New(8)) == NULL)
+        return VIR_PY_NONE;
     PyTuple_SetItem(info, 0, PyLong_FromLongLong(stats.rx_bytes));
     PyTuple_SetItem(info, 1, PyLong_FromLongLong(stats.rx_packets));
     PyTuple_SetItem(info, 2, PyLong_FromLongLong(stats.rx_errs));
@@ -114,12 +117,11 @@ libvirt_virGetLastError(PyObject *self ATTRIBUTE_UNUSED, PyObject *args ATTRIBUT
     virError err;
     PyObject *info;
 
-    if (virCopyLastError(&err) <= 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (virCopyLastError(&err) <= 0)
+        return VIR_PY_NONE;
 
-    info = PyTuple_New(9);
+    if ((info = PyTuple_New(9)) == NULL)
+        return VIR_PY_NONE;
     PyTuple_SetItem(info, 0, PyInt_FromLong((long) err.code));
     PyTuple_SetItem(info, 1, PyInt_FromLong((long) err.domain));
     PyTuple_SetItem(info, 2, libvirt_constcharPtrWrap(err.message));
@@ -145,12 +147,11 @@ libvirt_virConnGetLastError(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
         return(NULL);
     conn = (virConnectPtr) PyvirConnect_Get(pyobj_conn);
 
-    if (virConnCopyLastError(conn, &err) <= 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (virConnCopyLastError(conn, &err) <= 0)
+        return VIR_PY_NONE;
 
-    info = PyTuple_New(9);
+    if ((info = PyTuple_New(9)) == NULL)
+        return VIR_PY_NONE;
     PyTuple_SetItem(info, 0, PyInt_FromLong((long) err.code));
     PyTuple_SetItem(info, 1, PyInt_FromLong((long) err.domain));
     PyTuple_SetItem(info, 2, libvirt_constcharPtrWrap(err.message));
@@ -348,10 +349,8 @@ libvirt_virConnectOpenAuth(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
     if (auth.ncredtype) {
         int i;
         auth.credtype = malloc(sizeof(*auth.credtype) * auth.ncredtype);
-        if (auth.credtype == NULL) {
-            Py_INCREF(Py_None);
-            return (Py_None);
-        }
+        if (auth.credtype == NULL)
+            return VIR_PY_NONE;
         for (i = 0 ; i < auth.ncredtype ; i++) {
             PyObject *val;
             val = PyList_GetItem(pycredtype, i);
@@ -395,10 +394,8 @@ libvirt_virGetVersion (PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
 
     LIBVIRT_END_ALLOW_THREADS;
 
-    if (c_retval == -1) {
-        Py_INCREF(Py_None);
-        return (Py_None);
-    }
+    if (c_retval == -1)
+        return VIR_PY_NONE;
 
     if (type == NULL)
         return PyInt_FromLong (libVer);
@@ -458,10 +455,8 @@ libvirt_virConnectListDomainsID(PyObject *self ATTRIBUTE_UNUSED,
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virConnectListDomains(conn, &ids[0], 500);
     LIBVIRT_END_ALLOW_THREADS;
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     py_retval = PyList_New(c_retval);
     for (i = 0;i < c_retval;i++) {
         PyList_SetItem(py_retval, i, libvirt_intWrap(ids[i]));
@@ -484,22 +479,17 @@ libvirt_virConnectListDefinedDomains(PyObject *self ATTRIBUTE_UNUSED,
     conn = (virConnectPtr) PyvirConnect_Get(pyobj_conn);
 
     c_retval = virConnectNumOfDefinedDomains(conn);
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-        return (Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     
     if (c_retval) {
         names = malloc(sizeof(*names) * c_retval);
-        if (!names) {
-            Py_INCREF(Py_None);
-            return (Py_None);
-        }
+        if (!names)
+            return VIR_PY_NONE;
         c_retval = virConnectListDefinedDomains(conn, names, c_retval);
         if (c_retval < 0) {
             free(names);
-            Py_INCREF(Py_None);
-            return(Py_None);
+            return VIR_PY_NONE;
         }
     }
     py_retval = PyList_New(c_retval);
@@ -530,10 +520,8 @@ libvirt_virDomainGetInfo(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virDomainGetInfo(domain, &info);
     LIBVIRT_END_ALLOW_THREADS;
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     py_retval = PyList_New(5);
     PyList_SetItem(py_retval, 0, libvirt_intWrap((int) info.state));
     PyList_SetItem(py_retval, 1, libvirt_ulongWrap(info.maxMem));
@@ -559,10 +547,8 @@ libvirt_virNodeGetInfo(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virNodeGetInfo(conn, &info);
     LIBVIRT_END_ALLOW_THREADS;
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     py_retval = PyList_New(8);
     PyList_SetItem(py_retval, 0, libvirt_constcharPtrWrap(&info.model[0]));
     PyList_SetItem(py_retval, 1, libvirt_longWrap((long) info.memory >> 10));
@@ -587,18 +573,14 @@ libvirt_virDomainGetUUID(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
         return(NULL);
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
-    if (domain == NULL) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (domain == NULL)
+        return VIR_PY_NONE;
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virDomainGetUUID(domain, &uuid[0]);
     LIBVIRT_END_ALLOW_THREADS;
 
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0) 
+        return VIR_PY_NONE;
     py_retval = PyString_FromStringAndSize((char *) &uuid[0], VIR_UUID_BUFLEN);
 
     return(py_retval);
@@ -617,10 +599,8 @@ libvirt_virDomainLookupByUUID(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
         return(NULL);
     conn = (virConnectPtr) PyvirConnect_Get(pyobj_conn);
 
-    if ((uuid == NULL) || (len != VIR_UUID_BUFLEN)) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if ((uuid == NULL) || (len != VIR_UUID_BUFLEN))
+        return VIR_PY_NONE;
 
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virDomainLookupByUUID(conn, uuid);
@@ -664,22 +644,17 @@ libvirt_virConnectListNetworks(PyObject *self ATTRIBUTE_UNUSED,
     conn = (virConnectPtr) PyvirConnect_Get(pyobj_conn);
 
     c_retval = virConnectNumOfNetworks(conn);
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-        return (Py_None);
-    }
-    
+    if (c_retval < 0)
+        return VIR_PY_NONE;
+
     if (c_retval) {
         names = malloc(sizeof(*names) * c_retval);
-        if (!names) {
-            Py_INCREF(Py_None);
-            return (Py_None);
-        }
+        if (!names)
+            return VIR_PY_NONE;
         c_retval = virConnectListNetworks(conn, names, c_retval);
         if (c_retval < 0) {
             free(names);
-            Py_INCREF(Py_None);
-            return(Py_None);
+            return VIR_PY_NONE;
         }
     }
     py_retval = PyList_New(c_retval);
@@ -711,22 +686,17 @@ libvirt_virConnectListDefinedNetworks(PyObject *self ATTRIBUTE_UNUSED,
     conn = (virConnectPtr) PyvirConnect_Get(pyobj_conn);
 
     c_retval = virConnectNumOfDefinedNetworks(conn);
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-        return (Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     
     if (c_retval) {
         names = malloc(sizeof(*names) * c_retval);
-        if (!names) {
-            Py_INCREF(Py_None);
-            return (Py_None);
-        }
+        if (!names)
+            return VIR_PY_NONE;
         c_retval = virConnectListDefinedNetworks(conn, names, c_retval);
         if (c_retval < 0) {
             free(names);
-            Py_INCREF(Py_None);
-            return(Py_None);
+            return VIR_PY_NONE;
         }
     }
     py_retval = PyList_New(c_retval);
@@ -755,18 +725,14 @@ libvirt_virNetworkGetUUID(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
         return(NULL);
     domain = (virNetworkPtr) PyvirNetwork_Get(pyobj_domain);
 
-    if (domain == NULL) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (domain == NULL)
+        return VIR_PY_NONE;
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virNetworkGetUUID(domain, &uuid[0]);
     LIBVIRT_END_ALLOW_THREADS;
 
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     py_retval = PyString_FromStringAndSize((char *) &uuid[0], VIR_UUID_BUFLEN);
 
     return(py_retval);
@@ -785,10 +751,8 @@ libvirt_virNetworkLookupByUUID(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
         return(NULL);
     conn = (virConnectPtr) PyvirConnect_Get(pyobj_conn);
 
-    if ((uuid == NULL) || (len != VIR_UUID_BUFLEN)) {
-        Py_INCREF(Py_None);
-	return(Py_None);
-    }
+    if ((uuid == NULL) || (len != VIR_UUID_BUFLEN))
+        return VIR_PY_NONE;
 
     LIBVIRT_BEGIN_ALLOW_THREADS;
     c_retval = virNetworkLookupByUUID(conn, uuid);
@@ -814,10 +778,8 @@ libvirt_virDomainGetAutostart(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
     c_retval = virDomainGetAutostart(domain, &autostart);
     LIBVIRT_END_ALLOW_THREADS;
 
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return Py_None;
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     py_retval = libvirt_intWrap(autostart);
     return(py_retval);
 }
@@ -839,10 +801,8 @@ libvirt_virNetworkGetAutostart(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
     c_retval = virNetworkGetAutostart(network, &autostart);
     LIBVIRT_END_ALLOW_THREADS;
 
-    if (c_retval < 0) {
-        Py_INCREF(Py_None);
-	return Py_None;
-    }
+    if (c_retval < 0)
+        return VIR_PY_NONE;
     py_retval = libvirt_intWrap(autostart);
     return(py_retval);
 }
@@ -873,10 +833,9 @@ PyObject * libvirt_virNodeGetCellsFreeMemory(PyObject *self ATTRIBUTE_UNUSED,
     LIBVIRT_END_ALLOW_THREADS;
 
     if (c_retval < 0) {
-	free(freeMems);
+        free(freeMems);
 error:
-        Py_INCREF(Py_None);
-	return Py_None;
+        return VIR_PY_NONE;
     }
     py_retval = PyList_New(c_retval);
     for (i = 0;i < c_retval;i++) {
-- 
1.5.4.rc3.14.g44397


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