[FFmpeg-devel] [PATCH] Fix pkg-config detection when using a cross-prefix

[Kyle Schwarz]

On 7/2/2012 1:03 PM, Michael Niedermayer wrote:
> On Fri, Jun 29, 2012 at 10:08:06PM -0400, Kyle Schwarz wrote:
>> On 6/29/2012 11:04 AM, Michael Niedermayer wrote:
>>> On Fri, Jun 29, 2012 at 10:58:28AM -0400, Derek Buitenhuis wrote:
>>>> On 29/06/2012 2:30 AM, Kyle Schwarz wrote:
>>>>> The attached patch resolves a pkg-config issue.
>>>>>
>>>>> When a cross-prefix is used, FFmpeg searches for a cross-prefixed
>>>>> pkg-config, and fails to use pkg-config if none if found.
>>>>>
>>>>> This patch allows a native system pkg-config to be used if a prefixed
>>>>> one is not found.
>>>>
>>>> This seems like it could go quite wrong in some situations...
>>>
>>> seconded
>>
>> Can you give me an example of when it could go bad?
>
>
> assume you have libfoo 0.1 installed on your host and you cross
> compile and link to libfoo 9.0.
> the hosts pkg-config will search the hosts .pc files which will
> contain "instructions" to link to libfoo 0.1. Thes 2 libs may depend
> on different other libs, need different linker flags and be in
> different directories

The PKG_CONFIG_PATH is what controls where the .pc files are found.

> The problem i see is not using the hosts pkg-config but rather the
> hosts installed .pc files. But the hosts pkg-config will use them
> by default and i dont see something that would prevent it

As long as the PKG_CONFIG_PATH is set properly the host system libs will 
not be used.

Also, all users that cross compile are already aware of this and set the 
PKG_CONFIG_PATH already. This patch does not introduce anything new, it 
simply gets rid of unneeded options. Cross compilers are forces to do:
pkg_config=pkg-config
--pkg-config=pkg-config

Or a ln -s link to a fake cross prefixed pkg-config, to the native one.

All these unneeded options force FFmpeg to use the native pkg-config anyway.

Best regards,
   Kyle Schwarz