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Re: [Qemu-devel] [PATCH] fix qdev_print_devinfo()
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH] fix qdev_print_devinfo() |
Date: |
Mon, 03 Aug 2009 12:52:28 +0200 |
User-agent: |
Gnus/5.11 (Gnus v5.11) Emacs/22.3 (gnu/linux) |
Gerd Hoffmann <address@hidden> writes:
> snprintf returns number of bytes needed for the output, not the number
> of bytes actually written. Thus the math is wrong ...
>
> Spotted by Markus Armbruster.
>
> Signed-off-by: Gerd Hoffmann <address@hidden>
> ---
> hw/qdev.c | 26 +++++++++++++++++---------
> 1 files changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/hw/qdev.c b/hw/qdev.c
> index 9488dba..fc95115 100644
> --- a/hw/qdev.c
> +++ b/hw/qdev.c
> @@ -108,15 +108,23 @@ DeviceState *qdev_create(BusState *bus, const char
> *name)
> static int qdev_print_devinfo(DeviceInfo *info, char *dest, int len)
> {
> int pos = 0;
> + int ret;
>
> - pos += snprintf(dest+pos, len-pos, "name \"%s\", bus %s",
> - info->name, info->bus_info->name);
> - if (info->alias)
> - pos += snprintf(dest+pos, len-pos, ", alias \"%s\"", info->alias);
> - if (info->desc)
> - pos += snprintf(dest+pos, len-pos, ", desc \"%s\"", info->desc);
> - if (info->no_user)
> - pos += snprintf(dest+pos, len-pos, ", no-user");
> + ret = snprintf(dest+pos, len-pos, "name \"%s\", bus %s",
> + info->name, info->bus_info->name);
> + pos += MIN(len-pos,ret);
> + if (info->alias) {
> + ret = snprintf(dest+pos, len-pos, ", alias \"%s\"", info->alias);
> + pos += MIN(len-pos,ret);
> + }
> + if (info->desc) {
> + ret = snprintf(dest+pos, len-pos, ", desc \"%s\"", info->desc);
> + pos += MIN(len-pos,ret);
> + }
> + if (info->no_user) {
> + ret = snprintf(dest+pos, len-pos, ", no-user");
> + pos += MIN(len-pos,ret);
> + }
> return pos;
> }
Looks good.
For a general purpose formatting function, I'd return how much buffer is
needed to avoid truncation, just like snprintf(), to let the caller
resize its buffer. But qdev_print_devinfo()'s callers don't care.