[FFmpeg-cvslog] r15595 - trunk/libavcodec/aac_parser.c

[Måns Rullgård]

Baptiste Coudurier <baptiste.coudurier at gmail.com> writes:

> Michael Niedermayer wrote:
>> On Tue, Dec 02, 2008 at 12:05:43AM +0000, M?ns Rullg?rd wrote:
>>> Michael Niedermayer <michaelni at gmx.at> writes:
>>>
>>>> On Sat, Oct 11, 2008 at 01:21:45PM +0200, mru wrote:
>>>>> Author: mru
>>>>> Date: Sat Oct 11 13:21:45 2008
>>>>> New Revision: 15595
>>>>>
>>>>> Log:
>>>>> aac_parser: fix strict aliasing violation
>>>> This change is insufficient, the code still is not working without
>>>> -fno-strict-aliasing
>>>>
>>>> gcc-4.3
>>>>         .loc 1 37 0
>>>>         movl    %eax, -12(%ebp)
>>>> -       movl    %edx, -16(%ebp)
>>>>         .loc 62 42 0
>>>>         movl    -15(%ebp), %eax
>>>>
>>>> gcc-4.4
>>>>         .loc 1 37 0
>>>> -       movl    %edx, -16(%ebp)
>>>>         movl    %eax, -12(%ebp)
>>>>         .loc 62 42 0
>>>>         movl    -15(%ebp), %eax
>>> Damn.  It worked with all compilers I had installed at the time.  Can
>>> you think of a solution?
>> 
>> in order of most ugly to least
>> 1. lots and more union
>> 2. randomly change the code until it works with the current gccs
>> 3. pick another bitstream reader, i think ones that read bytes should work,
>>    but i did not test this
>> 4. add -fno-strict-aliasing to aac_parser.c (and possibly ac3_parser.c)
>>    compilation flags
>
> My 2 cents: do you know why this does not happen with ac3 parser ?

Because there's a function call there preventing the compiler from
seeing this "optimisation".

-- 
M?ns Rullg?rd
mans at mansr.com