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From: Paolo Bonzini <pbonzini@redhat.com>
To: Amos Kong <akong@redhat.com>, qemu-trivial@nongnu.org
Cc: qemu-devel@nongnu.org, afaerber@suse.de, jen@redhat.com,
	aliguori@amazon.com
Subject: Re: [Qemu-trivial] [PATCH] qom: suppress conscan warning of returning null point
Date: Sat, 20 Sep 2014 08:24:26 +0200	[thread overview]
Message-ID: <541D1D9A.6020100@redhat.com> (raw)
In-Reply-To: <1411171901-13792-1-git-send-email-akong@redhat.com>

Il 20/09/2014 02:11, Amos Kong ha scritto:
> Conscan complains about g_malloc0() and malloc() return null.
> 
>   Error: NULL_RETURNS (CWE-476):
>   qemu-kvm/qom/object.c:239: returned_null: Function "g_malloc0(gsize)" returns null.
>   qemu-kvm/qom/object.c:239: var_assigned: Assigning: "ti->class" = null return value from "g_malloc0(gsize)".
>   qemu-kvm/qom/object.c:249: dereference: Dereferencing a null pointer "ti->class".
> 
> But if the passed size parameter is >= 1, then we can always get an
> effective pointer, the warning disappears.

The model should handle it:

void *
g_malloc0(size_t n_bytes)
{
    void *mem;
    __coverity_negative_sink__(n_bytes);
    mem = calloc(1, n_bytes == 0 ? 1 : n_bytes);
    if (!mem) __coverity_panic__();
    return mem;
}

So this patch means your coverity runs are misconfigured.

Paolo


WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Amos Kong <akong@redhat.com>, qemu-trivial@nongnu.org
Cc: qemu-devel@nongnu.org, afaerber@suse.de, jen@redhat.com,
	aliguori@amazon.com
Subject: Re: [Qemu-devel] [PATCH] qom: suppress conscan warning of returning null point
Date: Sat, 20 Sep 2014 08:24:26 +0200	[thread overview]
Message-ID: <541D1D9A.6020100@redhat.com> (raw)
In-Reply-To: <1411171901-13792-1-git-send-email-akong@redhat.com>

Il 20/09/2014 02:11, Amos Kong ha scritto:
> Conscan complains about g_malloc0() and malloc() return null.
> 
>   Error: NULL_RETURNS (CWE-476):
>   qemu-kvm/qom/object.c:239: returned_null: Function "g_malloc0(gsize)" returns null.
>   qemu-kvm/qom/object.c:239: var_assigned: Assigning: "ti->class" = null return value from "g_malloc0(gsize)".
>   qemu-kvm/qom/object.c:249: dereference: Dereferencing a null pointer "ti->class".
> 
> But if the passed size parameter is >= 1, then we can always get an
> effective pointer, the warning disappears.

The model should handle it:

void *
g_malloc0(size_t n_bytes)
{
    void *mem;
    __coverity_negative_sink__(n_bytes);
    mem = calloc(1, n_bytes == 0 ? 1 : n_bytes);
    if (!mem) __coverity_panic__();
    return mem;
}

So this patch means your coverity runs are misconfigured.

Paolo

  parent reply	other threads:[~2014-09-20  6:25 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-20  0:11 [Qemu-trivial] [PATCH] qom: suppress conscan warning of returning null point Amos Kong
2014-09-20  0:11 ` [Qemu-devel] " Amos Kong
2014-09-20  2:41 ` [Qemu-trivial] " Gonglei (Arei)
2014-09-20  2:41   ` Gonglei (Arei)
2014-09-20  6:24 ` Paolo Bonzini [this message]
2014-09-20  6:24   ` Paolo Bonzini
2014-09-22  6:35   ` [Qemu-trivial] " Markus Armbruster
2014-09-22  6:35     ` Markus Armbruster

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