build: enforce reference count checking

Add the compiler attribute to ensure we don't introduce any more
ref bugs like were just patched in commit 9741f34, then explicitly
mark the remaining places in code that are safe.

* src/qemu/qemu_monitor.h (qemuMonitorUnref): Mark
ATTRIBUTE_RETURN_CHECK.
* src/conf/domain_conf.h (virDomainObjUnref): Likewise.
* src/conf/domain_conf.c (virDomainObjParseXML)
(virDomainLoadStatus): Fix offenders.
* src/openvz/openvz_conf.c (openvzLoadDomains): Likewise.
* src/vmware/vmware_conf.c (vmwareLoadDomains): Likewise.
* src/qemu/qemu_domain.c (qemuDomainObjBeginJob)
(qemuDomainObjBeginJobWithDriver)
(qemuDomainObjExitRemoteWithDriver): Likewise.
* src/qemu/qemu_monitor.c (QEMU_MONITOR_CALLBACK): Likewise.
Suggested by Daniel P. Berrange.

src/conf/domain_conf.c

@@ -6015,7 +6015,8 @@ static virDomainObjPtr virDomainObjParseXML(virCapsPtr caps,
     return obj;
 
 error:
-    virDomainObjUnref(obj);
+    /* obj was never shared, so unref should return 0 */
+    ignore_value(virDomainObjUnref(obj));
     return NULL;
 }
 
@@ -8220,8 +8221,9 @@ static virDomainObjPtr virDomainLoadStatus(virCapsPtr caps,
     return obj;
 
 error:
+    /* obj was never shared, so unref should return 0 */
     if (obj)
-        virDomainObjUnref(obj);
+        ignore_value(virDomainObjUnref(obj));
     VIR_FREE(statusFile);
     return NULL;
 }

src/conf/domain_conf.h

@@ -1206,7 +1206,7 @@ int virDomainDeviceInfoIterate(virDomainDefPtr def,
 void virDomainDefFree(virDomainDefPtr vm);
 void virDomainObjRef(virDomainObjPtr vm);
 /* Returns 1 if the object was freed, 0 if more refs exist */
-int virDomainObjUnref(virDomainObjPtr vm);
+int virDomainObjUnref(virDomainObjPtr vm) ATTRIBUTE_RETURN_CHECK;
 
 /* live == true means def describes an active domain (being migrated or
  * restored) as opposed to a new persistent configuration of the domain */

src/openvz/openvz_conf.c

@@ -1,7 +1,7 @@
 /*
  * openvz_conf.c: config functions for managing OpenVZ VEs
  *
- * Copyright (C) 2010 Red Hat, Inc.
+ * Copyright (C) 2010-2011 Red Hat, Inc.
  * Copyright (C) 2006, 2007 Binary Karma
  * Copyright (C) 2006 Shuveb Hussain
  * Copyright (C) 2007 Anoop Joe Cyriac
@@ -52,6 +52,7 @@
 #include "nodeinfo.h"
 #include "files.h"
 #include "command.h"
+#include "ignore-value.h"
 
 #define VIR_FROM_THIS VIR_FROM_OPENVZ
 
@@ -543,8 +544,9 @@ int openvzLoadDomains(struct openvz_driver *driver) {
  cleanup:
     virCommandFree(cmd);
     VIR_FREE(outbuf);
+    /* dom hasn't been shared yet, so unref should return 0 */
     if (dom)
-        virDomainObjUnref(dom);
+        ignore_value(virDomainObjUnref(dom));
     return -1;
 }
 

src/qemu/qemu_domain.c

@@ -31,6 +31,7 @@
 #include "c-ctype.h"
 #include "event.h"
 #include "cpu/cpu.h"
+#include "ignore-value.h"
 
 #include <sys/time.h>
 
@@ -460,7 +461,8 @@ int qemuDomainObjBeginJob(virDomainObjPtr obj)
 
     while (priv->jobActive) {
         if (virCondWaitUntil(&priv->jobCond, &obj->lock, then) < 0) {
-            virDomainObjUnref(obj);
+            /* Safe to ignore value since ref count was incremented above */
+            ignore_value(virDomainObjUnref(obj));
             if (errno == ETIMEDOUT)
                 qemuReportError(VIR_ERR_OPERATION_TIMEOUT,
                                 "%s", _("cannot acquire state change lock"));
@@ -504,7 +506,8 @@ int qemuDomainObjBeginJobWithDriver(struct qemud_driver *driver,
 
     while (priv->jobActive) {
         if (virCondWaitUntil(&priv->jobCond, &obj->lock, then) < 0) {
-            virDomainObjUnref(obj);
+            /* Safe to ignore value since ref count was incremented above */
+            ignore_value(virDomainObjUnref(obj));
             if (errno == ETIMEDOUT)
                 qemuReportError(VIR_ERR_OPERATION_TIMEOUT,
                                 "%s", _("cannot acquire state change lock"));
@@ -650,7 +653,9 @@ void qemuDomainObjExitRemoteWithDriver(struct qemud_driver *driver,
 {
     qemuDriverLock(driver);
     virDomainObjLock(obj);
-    virDomainObjUnref(obj);
+    /* Safe to ignore value, since we incremented ref in
+     * qemuDomainObjEnterRemoteWithDriver */
+    ignore_value(virDomainObjUnref(obj));
 }
 
 

src/qemu/qemu_monitor.c

@@ -763,7 +763,7 @@ int qemuMonitorHMPCommandWithFd(qemuMonitorPtr mon,
         if ((mon)->cb && (mon)->cb->callback)                   \
             (ret) = ((mon)->cb->callback)(mon, __VA_ARGS__);    \
         qemuMonitorLock(mon);                                   \
-        qemuMonitorUnref(mon);                                  \
+        ignore_value(qemuMonitorUnref(mon));                    \
     } while (0)
 
 int qemuMonitorGetDiskSecret(qemuMonitorPtr mon,

src/qemu/qemu_monitor.h

@@ -133,7 +133,7 @@ void qemuMonitorLock(qemuMonitorPtr mon);
 void qemuMonitorUnlock(qemuMonitorPtr mon);
 
 int qemuMonitorRef(qemuMonitorPtr mon);
-int qemuMonitorUnref(qemuMonitorPtr mon);
+int qemuMonitorUnref(qemuMonitorPtr mon) ATTRIBUTE_RETURN_CHECK;
 
 /* These APIs are for use by the internal Text/JSON monitor impl code only */
 int qemuMonitorSend(qemuMonitorPtr mon,

src/qemu/qemu_process.c

@@ -643,8 +643,9 @@ qemuConnectMonitor(struct qemud_driver *driver, virDomainObjPtr vm)
                                 priv->monJSON,
                                 &monitorCallbacks);
 
+    /* Safe to ignore value since ref count was incremented above */
     if (priv->mon == NULL)
-        virDomainObjUnref(vm);
+        ignore_value(virDomainObjUnref(vm));
 
     if (virSecurityManagerClearSocketLabel(driver->securityManager, vm) < 0) {
         VIR_ERROR(_("Failed to clear security context for monitor for %s"),

src/vmware/vmware_conf.c

@@ -1,5 +1,7 @@
 /*---------------------------------------------------------------------------*/
-/* Copyright 2010, diateam (www.diateam.net)
+/*
+ * Copyright (C) 2011 Red Hat, Inc.
+ * Copyright 2010, diateam (www.diateam.net)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -201,8 +203,9 @@ cleanup:
     VIR_FREE(directoryName);
     VIR_FREE(fileName);
     VIR_FREE(vmx);
+    /* any non-NULL vm here has not been shared, so unref will return 0 */
     if (vm)
-        virDomainObjUnref(vm);
+        ignore_value(virDomainObjUnref(vm));
     return ret;
 }