[FFmpeg-devel] (MSVC++) warning LNK4248: unresolved typeref token (01000015) for 'AVDictionary'; image may not run

[Reimar Döffinger]

On 22 Feb 2012, at 21:52, Matthew Einhorn <moiein2000 at gmail.com> wrote:
> On Wed, Feb 22, 2012 at 3:19 PM, John Dexter <jdxsolutions at gmail.com> wrote:
> 
>> I've just got ffmpeg working through MSVC++ 2008 using prebuilt libs,
>> everything seems to be working in my test project but I get this one
>> linker error and have no idea if it's a problem.
>> 
>> Is this normal, should I worry, etc?
>> 
>> warning LNK4248: unresolved typeref token (01000015) for
>> 'AVDictionary'; image may not run
>> 

Since it is a warning it is not a linker error.

> Without seeing source I can not be sure. But I suspect the problem arises
> because AVDictionary is not actually defined (other than a declaration) in
> the include files included with the dll dist.
> If you look in dict.h you'll see only this: "typedef struct AVDictionary
> AVDictionary;"
> 
> So, somewhere in your include files actually define AVDictionary as such:
> 
> //common.h
> struct AVDictionary {
>    int count;
>    AVDictionaryEntry *elems;
> };

If you do that your code an break at any time with any FFmpeg update.
We make no promises on the internal format of the AVDictionary struct.
I haven't been able to understand what the MSDN description of the warning is trying to say, but it sounds like it's an issue with CLR (i.e. managed code) interoperability.
In that case you just should make sure to not use that type from managed code (that probably actually applies to all FFmpeg types, e.g. you are not allowed to make assumptions on the size of AVCodecContext, but the managed code interop most likely will).