[FFmpeg-devel] [PATCH] libavutil: cast truncated values to uint32_t

[Reimar Döffinger]

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.