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From: malc <av1474@comtv.ru>
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Date: Fri, 16 Jan 2009 22:32:34 +0000
Subject: [Qemu-devel] [6359] Avoid calling qemu_mallocz with zero size
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Revision: 6359
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6359
Author:   malc
Date:     2009-01-16 22:32:33 +0000 (Fri, 16 Jan 2009)

Log Message:
-----------
Avoid calling qemu_mallocz with zero size

Currently qemu_mallocz calls malloc and handling of zero by malloc is
implementation defined behaviour:
http://www.opengroup.org/onlinepubs/7990989775/xsh/malloc.html

malloc(0) on AIX returns NULL[1] and qcow2 images without snapshots
are thus unusable

[1] Unless special Linux compatibility define is used when compiling

Modified Paths:
--------------
    trunk/block-qcow2.c

Modified: trunk/block-qcow2.c
===================================================================
--- trunk/block-qcow2.c	2009-01-16 21:48:20 UTC (rev 6358)
+++ trunk/block-qcow2.c	2009-01-16 22:32:33 UTC (rev 6359)
@@ -1809,6 +1809,12 @@
     int64_t offset;
     uint32_t extra_data_size;
 
+    if (!s->nb_snapshots) {
+        s->snapshots = NULL;
+        s->snapshots_size = 0;
+        return 0;
+    }
+
     offset = s->snapshots_offset;
     s->snapshots = qemu_mallocz(s->nb_snapshots * sizeof(QCowSnapshot));
     if (!s->snapshots)
@@ -2023,8 +2029,10 @@
     snapshots1 = qemu_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
     if (!snapshots1)
         goto fail;
-    memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
-    qemu_free(s->snapshots);
+    if (s->snapshots) {
+        memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
+        qemu_free(s->snapshots);
+    }
     s->snapshots = snapshots1;
     s->snapshots[s->nb_snapshots++] = *sn;