Re: [Buildroot] [PATCH 1/1] package/mjpg-streamer: fix undefined symbol error

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Bernd,

On Sun, 24 Mar 2024 19:56:59 +0100
Bernd Kuhls <bernd@kuhls.net> wrote:

> +diff --git a/mjpg-streamer-experimental/plugins/input_uvc/CMakeLists.txt b/mjpg-streamer-experimental/plugins/input_uvc/CMakeLists.txt
> +index 72b24fa..90bbfa0 100644
> +--- a/mjpg-streamer-experimental/plugins/input_uvc/CMakeLists.txt
> ++++ b/mjpg-streamer-experimental/plugins/input_uvc/CMakeLists.txt
> +@@ -22,6 +22,7 @@ if (PLUGIN_INPUT_UVC)
> +     MJPG_STREAMER_PLUGIN_COMPILE(input_uvc dynctrl.c
> +                                            input_uvc.c
> +                                            jpeg_utils.c
> ++                                           ../../utils.c
> +                                            v4l2uvc.c)

Thanks for the patch. Are you sure this is the right fix?

Indeed, the way I understand it is that there is a main executable
(mjpg-streamer), which loads using dlopen() a number of plugins. This
symbol resolutions_help is already provided by the mjpg-streamer main
executable itself, so why can't the dlopen()'ed plugin use it? Here
you're basically duplicating this symbol into the plugin itself. Is
that the right way to fix this issue? I am not sure 100% clear on what
are the rules that allow a dlopen() library to use the symbols of the
"thing" that dlopen()s the plugin, but it seems like it is possible.

Also, there is another plugin, input_opencv, which uses the exact same
symbol, so it would also need to be fixed.

Opinion from upstream here would be greatly appreciated to see how they
chose to design their code base.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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