Description:

Apparently, sdl2's cmake stuff has a bug and adds -DHAVE_LIBUDEV_H, while not compiling SDL_udev.c (or maybe not linking SDL_udev.o) into the output.

Additional info:
* SDL2 2.0.1-1
* Example output of a configure using sdl2:

cc -Wundef -Wall -Wno-switch -Wno-parentheses -Wpointer-arith -Wredundant-decls -Wstrict-prototypes -Wmissing-prototypes -Wdisabled-optimization -Wno-pointer-sign -std=gnu99 -O2 -g -pipe /tmp/mpv-configure-28520-25347/tmp.c -I. -D_GNU_SOURCE -I/usr/include/samba-4.0 -D_FORTIFY_SOURCE=2 -D_REENTRANT -I/usr/include/samba-4.0 -I/usr/include/quvi-0.9 -D_REENTRANT -I/usr/include/SDL2 -D_REENTRANT -pthread -I/usr/include/alsa -I/usr/include/freetype2 -I/usr/include/fribidi -I/usr/include/freetype2 -lncurses -lsmbclient -lquvi-0.9 -lwayland-client -lwayland-cursor -lxkbcommon -lXext -lX11 -lpthread -lrt -lXss -lXv -lvdpau -lva-x11 -lva -lXinerama -lXxf86vm -lcaca -lmng -lz -ljpeg -lGL -ldl -lwayland-egl -lwayland-client -lGL -lEGL -pthread -lSDL2 -lpulse -lportaudio -lasound -lm -lpthread -ljack -lpthread -lrt -lasound -lbluray -ldvdread -lcdio_paranoia -lcdio_cdda -lcdio -lm -lass -o /tmp/mpv-configure-28520-25347/tmp -lenca -lm
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libSDL2.so: undefined reference to `SDL_UDEV_Init'
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libSDL2.so: undefined reference to `SDL_UDEV_Quit'
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libSDL2.so: undefined reference to `SDL_UDEV_DelCallback'
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libSDL2.so: undefined reference to `SDL_UDEV_AddCallback'
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libSDL2.so: undefined reference to `SDL_UDEV_Poll'
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libSDL2.so: undefined reference to `SDL_UDEV_Scan'
collect2: error: ld returned 1 exit status

Obviously, libSDL2.so wants a symbol that SHOULD be defined in libSDL2.so itself, given its naming.

Adding -DHAVE_LIBUDEV_H=0 to the cmake arguments in the PKGBUILD fixes it for me (or rather, works around by turning off libudev support).

Severity "Critical" for this package as it makes the package totally useless; priority "Normal" is probably appropriate.