[asterisk-dev] [Code Review] 3734: media formats: Add a 'none' format to prevent NULL format derefences; update unit tests

[Matt Jordan]

> On July 9, 2014, 9:45 p.m., Corey Farrell wrote:
> > /team/group/media_formats-reviewed-trunk/main/format_cache.c, line 442
> > <https://reviewboard.asterisk.org/r/3734/diff/2/?file=62650#file62650line442>
> >
> >     I think just assert for !format.
> 
> Matt Jordan wrote:
>     No, this safety check is useful. It prevents someone from creating a named empty format and attempting to cache it.
>     
>     Making an API robust - particularly when those checks do not sit in a critical path - is not a bad thing :-)
> 
> Matt Jordan wrote:
>     On second thought, this is typically only used internally. An assert here is probably okay.

The name check is still appropriate: we shouldn't accept a named format that has no name.

You may ask: well, why not just check for that in the named format creation? And the answer is we should: but if someone changes that code, this should also flag the problem. Core APIs should be resistant to poor changes, such that future changes that introduce potential problems are more likely to get caught during peer review.


- Matt


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On July 9, 2014, 7:37 p.m., Matt Jordan wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/3734/
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> 
> (Updated July 9, 2014, 7:37 p.m.)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Repository: Asterisk
> 
> 
> Description
> -------
> 
> This patch does two things:
> 
> * It updates a few of the unit tests for some of the API changes. In particular, it focuses on adding some tests for formats with attributes and their expected behaviour. A few other non-format related unit tests were updated as well to handle off nominals detected during testing.
> 
> * It adds an 'ast_format_none' format. This format is a dummy format that can be used instead of a NULL pointer to prevent having to put NULL dereference checks into every place in the codebase. Channels are no assigned this format immediately upon creation, and their default capabilities are set to have it. As this format's codec has no translation (nor a representation in the RTP engine), it _shouldn't_ cause harm.
> 
> * A few NULL checks were put in anyway into key areas in a few modules. These were ones that were hit hard by the unit tests and prone to crashing if presented a NULL format.
> 
> 
> Diffs
> -----
> 
>   /team/group/media_formats-reviewed-trunk/tests/test_format_cap.c 418259 
>   /team/group/media_formats-reviewed-trunk/tests/test_format_cache.c 418259 
>   /team/group/media_formats-reviewed-trunk/tests/test_core_format.c 418259 
>   /team/group/media_formats-reviewed-trunk/tests/test_cel.c 418259 
>   /team/group/media_formats-reviewed-trunk/main/format_cap.c 418259 
>   /team/group/media_formats-reviewed-trunk/main/format_cache.c 418259 
>   /team/group/media_formats-reviewed-trunk/main/codec_builtin.c 418259 
>   /team/group/media_formats-reviewed-trunk/main/codec.c 418259 
>   /team/group/media_formats-reviewed-trunk/main/channel.c 418259 
>   /team/group/media_formats-reviewed-trunk/main/bridge_channel.c 418259 
>   /team/group/media_formats-reviewed-trunk/include/asterisk/format_cache.h 418259 
>   /team/group/media_formats-reviewed-trunk/include/asterisk/codec.h 418259 
> 
> Diff: https://reviewboard.asterisk.org/r/3734/diff/
> 
> 
> Testing
> -------
> 
> Unit tests pass.
> 
> There is a FRACK on shutdown, but it doesn't appear to be caused by this patch (things didn't run long enough without this patch before)
> 
> 
> Thanks,
> 
> Matt Jordan
> 
>

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