Re: [libvirt] [PATCH] remove useless code

[Jim Meyering <jim@xxxxxxxxxxxx>]

"Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote:
...
> These two are not safe to remove. Look at the whole code block in
> question:
>
>     if (diskVal->list == NULL)
>         VIR_FREE(diskVal);
>     else if (virConfSetValue(conf, "disk", diskVal) < 0) {
>         diskVal = NULL;
>         goto no_memory;
>     }
>     diskVal = NULL;
>
> In the case where virConfSetValue returned >= 0, we need to
> still set diskVal = NULL.

Oops.  Thanks.

However, the original code is ugly enough that I have rewritten
it to make it clear that regardless of the virConfSetValue outcome,
we don't free that variable:

    if (diskVal->list != NULL) {
        bool err = (virConfSetValue(conf, "disk", diskVal) < 0);
        diskVal = NULL;
        if (err)
            goto no_memory;
    }
    VIR_FREE(diskVal);

Here's the adjusted part of that c-set:

>From 2582d7c339e48e008f3f0066a30d3bd34cb7823e Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering@xxxxxxxxxx>
Date: Wed, 4 Feb 2009 17:44:24 +0100
Subject: [PATCH] remove useless code

* src/bridge.c (brAddTap): Remove redundant errno=ENOMEM assignment
after failed strdup.
* src/cgroup.c (virCgroupFree): Remove redundant *group=NULL assignment
after VIR_FREE(*group).
* src/lxc_driver.c (lxcShutdown): Likewise.
* src/xen_unified.c (xenUnifiedClose): Likewise.
* src/xm_internal.c (xenXMDomainConfigFormat): Rewrite disk-
and net-config-setting code to be clearer.
---
 src/bridge.c      |    6 ++----
 src/cgroup.c      |    1 -
 src/lxc_driver.c  |    1 -
 src/xen_unified.c |    1 -
 src/xm_internal.c |   21 ++++++++++-----------
 5 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/src/bridge.c b/src/bridge.c
...
diff --git a/src/xm_internal.c b/src/xm_internal.c
index a03263c..a6e0bee 100644
--- a/src/xm_internal.c
+++ b/src/xm_internal.c
@@ -2233,14 +2233,13 @@ virConfPtr xenXMDomainConfigFormat(virConnectPtr conn,
                                         hvm, priv->xendConfigVersion) < 0)
             goto cleanup;
     }
-    if (diskVal->list == NULL)
-        VIR_FREE(diskVal);
-    else if (virConfSetValue(conf, "disk", diskVal) < 0) {
+    if (diskVal->list != NULL) {
+        bool err = (virConfSetValue(conf, "disk", diskVal) < 0);
         diskVal = NULL;
-        goto no_memory;
+        if (err)
+            goto no_memory;
     }
-    diskVal = NULL;
-
+    VIR_FREE(diskVal);

     if (VIR_ALLOC(netVal) < 0)
         goto no_memory;
@@ -2253,13 +2252,13 @@ virConfPtr xenXMDomainConfigFormat(virConnectPtr conn,
                                        hvm) < 0)
             goto cleanup;
     }
-    if (netVal->list == NULL)
-        VIR_FREE(netVal);
-    else if (virConfSetValue(conf, "vif", netVal) < 0) {
+    if (netVal->list != NULL) {
+        bool err = (virConfSetValue(conf, "vif", netVal) < 0);
         netVal = NULL;
-        goto no_memory;
+        if (err)
+            goto no_memory;
     }
-    netVal = NULL;
+    VIR_FREE(netVal);

     if (hvm) {
         if (def->nparallels) {
--
1.6.1.2.511.gc5d3f

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