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From: Markus Armbruster <armbru@redhat.com>
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Date: Tue, 16 Sep 2014 18:24:44 +0200
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	(zhanghailiang's message of "Tue, 16 Sep 2014 15:30:59 +0800")
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Subject: Re: [Qemu-devel] [PATCH v5 2/2] dump: Don't return error code when
	return an Error object
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To: zhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: luonengjun@huawei.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, qiaonuohan@cn.fujitsu.com, peter.huangpeng@huawei.com, lersek@redhat.com

zhanghailiang <zhang.zhanghailiang@huawei.com> writes:

> Functions shouldn't return an error code and an Error object at the same time.
> Turn all these functions that returning Error object to void.
> We also judge if a function success or fail by reference to the *errp.
>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>  dump.c | 244 +++++++++++++++++++++++++----------------------------------------
>  1 file changed, 94 insertions(+), 150 deletions(-)
>
> diff --git a/dump.c b/dump.c
> index 07d2300..b2ed846 100644
> --- a/dump.c
> +++ b/dump.c
[...]
>  /* write the memroy to vmcore. 1 page per I/O. */
> -static int write_memory(DumpState *s, GuestPhysBlock *block, ram_addr_t start,
> +static void write_memory(DumpState *s, GuestPhysBlock *block, ram_addr_t start,
>                          int64_t size, Error **errp)
>  {
>      int64_t i;
> -    int ret;
>  
>      for (i = 0; i < size / TARGET_PAGE_SIZE; i++) {
> -        ret = write_data(s, block->host_addr + start + i * TARGET_PAGE_SIZE,
> +        write_data(s, block->host_addr + start + i * TARGET_PAGE_SIZE,
>                           TARGET_PAGE_SIZE, errp);

Please fix up indentation of arguments.

> -        if (ret < 0) {
> -            return ret;
> +        if (*errp) {
> +            return;

This breaks when a caller choses to ignore errors by passing a null
argument for errp.

For static functions that may be okay.  But in general, we support null
arguments by coding like this:

    Error *local_err = NULL;
    int64_t i;

    for (i = 0; i < size / TARGET_PAGE_SIZE; i++) {
        write_data(s, block->host_addr + start + i * TARGET_PAGE_SIZE,
                   TARGET_PAGE_SIZE, &local_err);
        if (local_err) {
            error_propagate(errp, local_err);
            return;
        }
    }

I feel it's better to stick to this convention.

More of the same elsewhere.

>          }
>      }
[...]