[Buildroot] [PATCH] ffmpeg: fix static linking build failure when using libavutil

[Giulio Benetti <giulio.benetti@micronovasrl.com>]

Hello,

Il 11/09/2018 22:42, Giulio Benetti ha scritto:
> When static linking programs using ffmpeg libraries, if linking against
> libavutil, -ldrm is listed before -lavutil. This leads to linking failure
> due to undefined reference of drmGetVersion() and drmFreeVersion().
> This is why when pkg-config generates libavutil.pc doesn't append -ldrm
> after -lavutil.
> Subsequentely if a package uses pkg-config and ffmpeg it will load
> library dependencies from libavutil.pc without placing -ldrm at the tail.
> Without this fix the only way is to workaround the problem directly in
> the single package, like this:
> https://github.com/buildroot/buildroot/commit/daf7dd87f4d93923df5e757fd43b3ad214a4a2ae
> 
> Add patch to assure -ldrm comes after -lavutil when static linking.
> 
> Fixes:
> http://autobuild.buildroot.net/results/515/5152dcca58944cf732d09fba6e6c9af8a9243c75//
> http://autobuild.buildroot.net/results/395/395be1a9cab824b82ef34c2ebd84d54243029b33//
> 
> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> ---
>   ...igure-add-LIBDRM-to-extralibs_avutil.patch | 44 +++++++++++++++++++
>   1 file changed, 44 insertions(+)
>   create mode 100644 package/ffmpeg/0002-configure-add-LIBDRM-to-extralibs_avutil.patch
> 
> diff --git a/package/ffmpeg/0002-configure-add-LIBDRM-to-extralibs_avutil.patch b/package/ffmpeg/0002-configure-add-LIBDRM-to-extralibs_avutil.patch
> new file mode 100644
> index 0000000000..ae1f3423ae
> --- /dev/null
> +++ b/package/ffmpeg/0002-configure-add-LIBDRM-to-extralibs_avutil.patch
> @@ -0,0 +1,44 @@
> +From f4c9a7f55229d5275edb89c29ac9b18a737faf65 Mon Sep 17 00:00:00 2001
> +From: Giulio Benetti <giulio.benetti@micronovasrl.com>
> +Date: Tue, 11 Sep 2018 19:22:27 +0200
> +Subject: [PATCH] configure: add LIBDRM to extralibs_avutil
> +
> +When static linking programs using ffmpeg libraries, if linking against
> +libavutil, -ldrm is listed before -lavutil. This leads to linking failure
> +due to undefined reference of drmGetVersion() and drmFreeVersion().
> +This is why when pkg-config create libavutil.pc doesn't append -ldrm
> +after -lavutil.
> +
> +Add -ldrm to LIBDRM in case libdrm is enabled and add $LIBDRM to
> +extralibs_avutil.
> +
> +Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> +---
> + configure | 4 ++--
> + 1 file changed, 2 insertions(+), 2 deletions(-)
> +
> +diff --git a/configure b/configure
> +index 7377046d0a..7599fcc2bd 100755
> +--- a/configure
> ++++ b/configure
> +@@ -5919,7 +5919,7 @@ enabled libcelt           && require libcelt celt/celt.h celt_decode -lcelt0 &&
> +                                die "ERROR: libcelt must be installed and version must be >= 0.11.0."; }
> + enabled libcaca           && require_pkg_config libcaca caca caca.h caca_create_canvas
> + enabled libdc1394         && require_pkg_config libdc1394 libdc1394-2 dc1394/dc1394.h dc1394_new
> +-enabled libdrm            && require_pkg_config libdrm libdrm xf86drm.h drmGetVersion
> ++enabled libdrm            && require_pkg_config libdrm libdrm xf86drm.h drmGetVersion && LIBDRM="-ldrm"
> + enabled libfdk_aac        && { use_pkg_config libfdk_aac fdk-aac "fdk-aac/aacenc_lib.h" aacEncOpen ||
> +                                { require libfdk_aac fdk-aac/aacenc_lib.h aacEncOpen -lfdk-aac &&
> +                                  warn "using libfdk without pkg-config"; } }
> +@@ -7096,7 +7096,7 @@ source_path=${source_path}
> + LIBPREF=${LIBPREF}
> + LIBSUF=${LIBSUF}
> +
> +-extralibs_avutil="$LIBRT $LIBM"
> ++extralibs_avutil="$LIBDRM $LIBRT $LIBM"
> + extralibs_avcodec="$extralibs"
> + extralibs_avformat="$extralibs"
> + extralibs_avdevice="$extralibs"
> +--
> +2.17.1
> +
> 

The patch above has been upstreamed:
https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/c50dc77ac708e98d02da7c422a6b9cbf9f565aa5

-- 
Giulio Benetti
CTO

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