[Buildroot] [PATCH] package/mesa3d: dri: link statically libmegadriver_stub after libdricommon

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

On Tue,  9 Jun 2020 17:20:07 +0200
Romain Naour <romain.naour@gmail.com> wrote:

> Meson build system enable by default -Wl,--as-needed in the linker command line [1] and
> due to this the megadriver_stub build can fail with some toolchain:
> 
> /home/buildroot/autobuild/run/instance-1/output-1/host/bin/arm-none-linux-gnueabi-g++
>   -o src/mesa/drivers/dri/libmesa_dri_drivers.so
>   -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -shared -fPIC -Wl,--start-group
>   -Wl,-soname,libmesa_dri_drivers.so -Wl,--whole-archive
>   src/mesa/drivers/dri/radeon/libr100.a src/mesa/drivers/dri/nouveau/libnouveau_vieux.a
>   -Wl,--no-whole-archive
>   src/mesa/drivers/dri/common/libmegadriver_stub.a
>   src/mesa/drivers/dri/common/libdricommon.a
>   src/mapi/shared-glapi/libglapi.so.0.0.0
>   src/mesa/libmesa_classic.a src/mesa/libmesa_common.a
>   src/compiler/glsl/libglsl.a src/compiler/glsl/glcpp/libglcpp.a
>   src/util/libmesa_util.a src/util/format/libmesa_format.a
>   src/compiler/nir/libnir.a src/compiler/libcompiler.a
>   src/util/libxmlconfig.a
>   [...]
> src/mesa/drivers/dri/common/libmegadriver_stub.a(megadriver_stub.c.o): In function `megadriver_stub_init':
> megadriver_stub.c:(.text.startup+0x20): undefined reference to `dladdr'
> megadriver_stub.c:(.text.startup+0xbc): undefined reference to `dlsym'
> collect2: error: ld returned 1 exit status
> 
> This is because the static librairies needs to be correcly sorted by dependency.
> libmegadriver_stub include dri_util.h that internally include dri_interface.h needed for
> dlsym and dladdr definition.
> 
> [1] https://mesonbuild.com/Builtin-options.html
> 
> Fixes:
> http://autobuild.buildroot.net/results/eec39a4fbfbfaa58980fab36f2fd902a16eecf0f/build-end.log
> 
> Signed-off-by: Romain Naour <romain.naour@gmail.com>
> ---
>  ...lly-libmegadriver_stub-after-libdric.patch | 58 +++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  create mode 100644 package/mesa3d/0009-dri-link-statically-libmegadriver_stub-after-libdric.patch
> 
> diff --git a/package/mesa3d/0009-dri-link-statically-libmegadriver_stub-after-libdric.patch b/package/mesa3d/0009-dri-link-statically-libmegadriver_stub-after-libdric.patch
> new file mode 100644
> index 0000000000..47909ed5e5
> --- /dev/null
> +++ b/package/mesa3d/0009-dri-link-statically-libmegadriver_stub-after-libdric.patch
> @@ -0,0 +1,58 @@
> +From b4f68629937eac22f122b9b069e4e5acbcc51a75 Mon Sep 17 00:00:00 2001
> +From: Romain Naour <romain.naour@gmail.com>
> +Date: Tue, 9 Jun 2020 16:49:32 +0200
> +Subject: [PATCH] dri: link statically libmegadriver_stub after libdricommon
> +
> +Meson build system enable by default -Wl,--as-needed in the linker command line [1] and
> +due to this the megadriver_stub build can fail with some toolchain:
> +
> +/home/buildroot/autobuild/run/instance-1/output-1/host/bin/arm-none-linux-gnueabi-g++
> +  -o src/mesa/drivers/dri/libmesa_dri_drivers.so
> +  -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -shared -fPIC -Wl,--start-group
> +  -Wl,-soname,libmesa_dri_drivers.so -Wl,--whole-archive
> +  src/mesa/drivers/dri/radeon/libr100.a src/mesa/drivers/dri/nouveau/libnouveau_vieux.a
> +  -Wl,--no-whole-archive
> +  src/mesa/drivers/dri/common/libmegadriver_stub.a
> +  src/mesa/drivers/dri/common/libdricommon.a
> +  src/mapi/shared-glapi/libglapi.so.0.0.0
> +  src/mesa/libmesa_classic.a src/mesa/libmesa_common.a
> +  src/compiler/glsl/libglsl.a src/compiler/glsl/glcpp/libglcpp.a
> +  src/util/libmesa_util.a src/util/format/libmesa_format.a
> +  src/compiler/nir/libnir.a src/compiler/libcompiler.a
> +  src/util/libxmlconfig.a
> +  [...]
> +src/mesa/drivers/dri/common/libmegadriver_stub.a(megadriver_stub.c.o): In function `megadriver_stub_init':
> +megadriver_stub.c:(.text.startup+0x20): undefined reference to `dladdr'
> +megadriver_stub.c:(.text.startup+0xbc): undefined reference to `dlsym'
> +collect2: error: ld returned 1 exit status
> +
> +This is because the static librairies needs to be correcly sorted by dependency.
> +libmegadriver_stub include dri_util.h that internally include dri_interface.h needed for
> +dlsym and dladdr definition.

Why do .h files matter here? This sort of linking issue really should
have nothing to do with header files inclusion/ordering, but just about
object file/library ordering at link time.

Could you clarify what is happening here? dladdr and dlsym are provided
by the C library, so I'm not sure why the ordering between libdricommon
and libmegadriver_stub can matter here.

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com