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Re: [Qemu-trivial] [Qemu-devel] [PATCH] get_tmp_filename: add explicit e

From: Fabien Chouteau
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] get_tmp_filename: add explicit error message
Date: Mon, 04 Feb 2013 14:33:18 +0100
User-agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2

On 02/04/2013 01:24 PM, Markus Armbruster wrote:
> Fabien Chouteau <address@hidden> writes:
>> On 02/04/2013 11:34 AM, Markus Armbruster wrote:
>> Why? The caller doesn't know the difference between Windows/Linux
>> implementation. And the error handling would have to be duplicated.
> The function's (implied) contract is to return an error code without
> printing anything.  If you want to change the contract to include
> reporting the error, you need to implement it both for both arms of the
> #ifdef.  You also have to demonstrate that all callers are happy with
> the change of contract.
> Regardless, printing to stderr is wrong.  The function can be called on
> behalf of a monitor command, and then the error needs to be printed to
> the correct monitor.  error_report() can do that for you, and more.

Alright, so I will use error_report() and do it for both Linux and Windows.

>> It's not the first time I add error output in Windows code. Specially in
>> block/, when there's an error, the only thing you get is: "operation not
>> permitted". It's not very helpful and you have to dig in the code to
>> find which function failed.
> Good error reporting is hard.  Knowledge about the error and its context
> gets lost as you move up the call chain.  Knowledge about how to report
> errors gets lost as you move down.

You're right, and in my opinion, no error reporting is the worst case.

Fabien Chouteau

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