[FFmpeg-devel] [PATCH 2/3] pmpdec: fix signedness

[Don Moir]

----- Original Message ----- 
From: "Reimar Döffinger" <Reimar.Doeffinger at gmx.de>
To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
Sent: Saturday, February 23, 2013 5:46 PM
Subject: Re: [FFmpeg-devel] [PATCH 2/3] pmpdec: fix signedness

> On 23 Feb 2013, at 22:08, Michael Niedermayer <michaelni at gmx.at> wrote:
>
>
>>> Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
>>> ---
>>> libavformat/pmpdec.c |    4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/libavformat/pmpdec.c b/libavformat/pmpdec.c
>>> index 358f7b6..38eba14 100644
>>> --- a/libavformat/pmpdec.c
>>> +++ b/libavformat/pmpdec.c
>>> @@ -44,7 +44,7 @@ static int pmp_header(AVFormatContext *s)
>>>     PMPContext *pmp = s->priv_data;
>>>     AVIOContext *pb = s->pb;
>>>     int tb_num, tb_den;
>>> -    int index_cnt;
>>> +    unsigned index_cnt;
>>>     int audio_codec_id = AV_CODEC_ID_NONE;
>>>     int srate, channels;
>>>     int i;
>>> @@ -93,7 +93,7 @@ static int pmp_header(AVFormatContext *s)
>>>     channels = avio_rl32(pb) + 1;
>>>     pos = avio_tell(pb) + 4*index_cnt;
>>>     for (i = 0; i < index_cnt; i++) {
>>> -        int size = avio_rl32(pb);
>>> +        unsigned size = avio_rl32(pb);

>> Why not go all the way and use uint32_t ?
>> Seems safest to do.
>> All patches look ok to me.

>By changing size and index_cnt to uint32_t it introduces 3 warnings for signed/unsigned mismatch for me when compiling that code in 
>Visual Studio. You don't see that in mingw. But more than that, it seems to me by keeping them as int you get an automatic check 
>for an out of bounds condition. That is, an exceesively large number will be negative and fail accordingly.

Also if index_cnt is a number greater than INT_MAX since it's now uint32_t and since ' i ' is an int, an endless loop will occur.

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