Re: [Qemu-devel] [PATCH for-2.12] dump: Fix build with newer gcc - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Eric Blake <eblake@redhat.com>, qemu-devel@nongnu.org
Cc: qemu-trivial@nongnu.org,
	"Marc-André Lureau" <marcandre.lureau@redhat.com>
Subject: Re: [Qemu-devel] [PATCH for-2.12] dump: Fix build with newer gcc
Date: Tue, 27 Mar 2018 17:36:47 -0300	[thread overview]
Message-ID: <3398457e-bd2a-8eaa-2157-a13c67b09c29@amsat.org> (raw)
In-Reply-To: <20180327202152.1799131-1-eblake@redhat.com>

On 03/27/2018 05:21 PM, Eric Blake wrote:
> gcc 8 on rawhide is picky enough to complain:
> 
> /home/dummy/qemu/dump.c: In function 'create_header32':
> /home/dummy/qemu/dump.c:817:5: error: 'strncpy' output truncated before terminating nul copying 8 bytes from a string of the same length [-Werror=stringop-truncation]
>      strncpy(dh->signature, KDUMP_SIGNATURE, strlen(KDUMP_SIGNATURE));
>      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> But we already have SIG_LEN defined as the right length without needing
> to do a strlen(), and memcpy() is better than strncpy() when we know
> we do not want a trailing NUL byte.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>  dump.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/dump.c b/dump.c
> index 669f715274d..b54cd42b217 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -814,7 +814,7 @@ static void create_header32(DumpState *s, Error **errp)
>      size = sizeof(DiskDumpHeader32);
>      dh = g_malloc0(size);
> 
> -    strncpy(dh->signature, KDUMP_SIGNATURE, strlen(KDUMP_SIGNATURE));
> +    memcpy(dh->signature, KDUMP_SIGNATURE, SIG_LEN);
>      dh->header_version = cpu_to_dump32(s, 6);
>      block_size = s->dump_info.page_size;
>      dh->block_size = cpu_to_dump32(s, block_size);
> @@ -926,7 +926,7 @@ static void create_header64(DumpState *s, Error **errp)
>      size = sizeof(DiskDumpHeader64);
>      dh = g_malloc0(size);
> 
> -    strncpy(dh->signature, KDUMP_SIGNATURE, strlen(KDUMP_SIGNATURE));
> +    memcpy(dh->signature, KDUMP_SIGNATURE, SIG_LEN);
>      dh->header_version = cpu_to_dump32(s, 6);
>      block_size = s->dump_info.page_size;
>      dh->block_size = cpu_to_dump32(s, block_size);
>