[FFmpeg-devel] [PATCH] libavutil: cast truncatedvaluestouint32_t

Don Moir donmoir at comcast.net
Tue Aug 27 06:13:49 CEST 2013

----- Original Message ----- 
From: "Don Moir" <donmoir at comcast.net>
To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
Sent: Monday, August 26, 2013 11:55 PM
Subject: Re: [FFmpeg-devel] [PATCH] libavutil: cast truncatedvaluestouint32_t

>> On 27.08.2013, at 04:47, "Don Moir" <donmoir at comcast.net> wrote:
>>> ----- Original Message ----- From: "Reimar Döffinger" <Reimar.Doeffinger at gmx.de>
>>> To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
>>> Sent: Monday, August 26, 2013 10:38 PM
>>> Subject: Re: [FFmpeg-devel] [PATCH] libavutil: cast truncated values touint32_t
>>>> On 27.08.2013, at 04:09, Michael Niedermayer <michaelni at gmx.at> wrote:
>>>>> On Mon, Aug 26, 2013 at 10:44:08PM +0200, Alfred E. Heggestad wrote:
>>>>>> common.h   |    4 ++--
>>>>>> rational.h |    2 +-
>>>>>> 2 files changed, 3 insertions(+), 3 deletions(-)
>>>>>> 62a4072f9a04e905abe285fc98ecb7baeacad63a  0001-libavutil-cast-truncated-values-to-uint32_t.patch
>>>>>> From fda5dcc3784be312a8242512a8df1e3dd197df77 Mon Sep 17 00:00:00 2001
>>>>>> From: "Alfred E. Heggestad" <aeh at db.org>
>>>>>> Date: Mon, 26 Aug 2013 22:31:43 +0200
>>>>>> Subject: [PATCH] libavutil: cast truncated values to uint32_t
>>>>>> programs using ffmpeg that are compiled with -Wshorten-64-to-32
>>>>>> gives a warning when using header files common.h and rational.h
>>>>>> cast 64-bit truncated values to (uint32_t) to avoid the warning
>>>>> compilers dont print warnings for problems in system headers, the
>>>>> libavutil headers are treated as such when installed.
>>>>> can you elaborate on why this compiler "feature" doesnt work in
>>>>> your case ?
>>>>> fixing all warnings that any compiler with any option wth any header
>>>>> could generate is not a trivial task and with some predantic warnings
>>>>> might even be impossible
>>>> Not to mention that in at least 2, if not all cases the compiler is being extremely stupid.
>>>> It's trivial to prove that the result fits in 32 bit and thus there is no reason to warn.
>>>> A compiler offering such an option should at least understand that (uint64 >> 32) fits in 32 bit.
>>> The point is this is trival and the only warnings I get with msc from ffmpeg headers. So everyone dealing with it who cares 
>>> turns the warnings off for ffmpeg which I don't like to do. It's reality and not to decide on compiler intelligence.
>> Even older MSVC versions should figure this out and not warn about it, it definitely understands >> 32 (and I am fairly certain 
>> that in the case of MSVC we discussed this before, and I believed that you agreed there was no issue, so why does this come up 
>> again on an unrelated gcc thing?).
>> And "fixing" these kind of things in every single piece of software when it could be fixed properly in the compiler isn't exactly 
>> the right way.
>> We usually expect at least bug reports to be opened before working around issues in other project's code. That is the only way to 
>> give better solutions at least a chance.
> I believe I reported it way back and then reported by others and on and on... Still get the same old answer... Since there is only 
> a few that generate such warnings in the public headers, seems it should be fixed in header. You can on about stupid compile but 
> thats not going to help and everyone can just deal with it. It's not a big deal but I would prefer not to disable the warnings and 
> everyone else can spend time dealing with it, reporting, or whatever.


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