(In reply to Gu Nini from comment #0)
> Additional info:
> Following patch already fix the bug, but not merged into latest QEMU 1.5.3
> version:
> http://git.qemu.org/?p=qemu.git;a=commitdiff;
> h=98cf48f60aa4999f5b2808569a193a401a390e6a

commit 98cf48f60aa4999f5b2808569a193a401a390e6a
Author: Paolo Bonzini <pbonzini>
Date:   Wed Sep 16 17:38:44 2015 +0200

    trace: remove malloc tracing
    
    The malloc vtable is not supported anymore in glib, because it broke
    when constructors called g_malloc.  Remove tracing of g_malloc,
    g_realloc and g_free calls.
    
    Note that, for systemtap users, glib also provides tracepoints
    glib.mem_alloc, glib.mem_free, glib.mem_realloc, glib.slice_alloc
    and glib.slice_free.
    
    Signed-off-by: Paolo Bonzini <pbonzini>
    Reviewed-by: Alberto Garcia <berto>
    Message-id: 1442417924-25831-1-git-send-email-pbonzini
    Signed-off-by: Stefan Hajnoczi <stefanha>

Found the same issue on rhel7.2z qemu-kvm-rhev versions:

[root@hp-z800-03 qemu-kvm]# rpm -qa|grep qemu
qemu-img-rhev-2.3.0-31.el7_2.20.x86_64
ipxe-roms-qemu-20160127-1.git6366fa7a.el7.noarch
qemu-kvm-tools-rhev-2.3.0-31.el7_2.20.x86_64
qemu-kvm-common-rhev-2.3.0-31.el7_2.20.x86_64
qemu-kvm-rhev-2.3.0-31.el7_2.20.x86_64
[root@hp-z800-03 qemu-kvm]# 
[root@hp-z800-03 qemu-kvm]# 
[root@hp-z800-03 qemu-kvm]# 
[root@hp-z800-03 qemu-kvm]# /usr/libexec/qemu-kvm -name 'avocado-vt-vm1' -vnc :0 -monitor stdio

(process:13902): GLib-WARNING **: gmem.c:482: custom memory allocation vtable not supported
QEMU 2.3.0 monitor - type 'help' for more information
(qemu)

Fix included in qemu-kvm-1.5.3-121.el7

Verify the bug on following sw versions:

Host kernel: 3.10.0-481.el7.x86_64
Qemu-kvm: qemu-kvm-1.5.3-121.el7.x86_64


There is no the warning prompt any more:
# /usr/libexec/qemu-kvm -name 'avocado-vt-vm1' -vnc :0 -monitor stdio
QEMU 1.5.3 monitor - type 'help' for more information
(qemu)

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2016-2585.html

*** Bug 1594304 has been marked as a duplicate of this bug. ***

can it be that this bug is only fixed for qemu-kvm, but not for qemu-system-x86_64

While trying to use packer from packer.io and qemu as builder I ran into:

2019/01/16 13:32:11 packer: 2019/01/16 13:32:11 Executing /usr/bin/qemu-system-x86_64: []string{"-vnc", "127.0.0.1:66", "-machine", "type=pc,accel=tcg", "-device", "virtio-net,netdev=user.0", "-name", "centos-vm", "-netdev", "user,id=user.0,hostfwd=tcp::3397-:22", "-cdrom", "/home/****/packer.io/configs/centos7/packer_cache/2c14e2204a6adb446f541f4437d9540f0972ed66637769c6527aea0242ec540f.iso", "-m", "512M", "-drive", "file=builds/centos-vm,if=virtio,cache=writeback,discard=ignore,format=qcow2", "-boot", "once=d", "-display", "sdl"}
2019/01/16 13:32:11 packer: 2019/01/16 13:32:11 Started Qemu. Pid: 50389
2019/01/16 13:32:11 packer: 2019/01/16 13:32:11 Qemu stderr:
2019/01/16 13:32:11 packer: 2019/01/16 13:32:11 Qemu stderr: (process:50389): GLib-WARNING **: 13:32:11.276: gmem.c:489: custom memory allocation vtable not supported
2019/01/16 13:32:11 packer: 2019/01/16 13:32:11 Qemu stderr: Could not initialize SDL(No available video device) - exiting
2019/01/16 13:32:11 ui error: ==> qemu: Error launching VM: Qemu failed to start. Please run with PACKER_LOG=1 to get more info.

rpm -qa |grep ^qemu
qemu-system-x86-2.0.0-1.el7.6.x86_64
qemu-img-1.5.3-160.el7.x86_64
qemu-kvm-1.5.3-160.el7.x86_64
qemu-common-2.0.0-1.el7.6.x86_64
qemu-kvm-common-1.5.3-160.el7.x86_64

System is RHEL 7.6

(In reply to Peter Bieringer from comment #11)
> can it be that this bug is only fixed for qemu-kvm, but not for
> qemu-system-x86_64
> 
> While trying to use packer from packer.io and qemu as builder I ran into:
> 


See https://bugzilla.redhat.com/show_bug.cgi?id=1666811#c1