[Mesa-dev] Meson links with duplicate symbols

[Jose Fonseca]

While reviewing my colleagues efforts to consume Meson for Windows I stumbled across two issues.

First is that even though we added the "WARNING: Scons support is in the process of being deprecated on on windows platforms (including mingw). If you haven't already please try using meson for windows builds. Be sure to report any issues you run into" to scons, we didn't update mesa/docs/install.html with instructions on how to build Meson w/ Mingw for windows, so it's not obvious to a newbie how to do it.  It took me quite a while to reverse engineer the stuff in .gitlab-ci/... till I figured out the way to do it.  I think that adding example command lines would go a long way.

Second and most important is that Meson is actually linking with duplicate symbols.  This was being hidden because meson doesn't use whole linking for everything, whereas SCons does.  It's easy to repro:

$ git diff
diff --git a/src/gallium/targets/libgl-gdi/meson.build b/src/gallium/targets/libgl-gdi/meson.build
index cd4e02d1fa9..fb8a42439c8 100644
--- a/src/gallium/targets/libgl-gdi/meson.build
+++ b/src/gallium/targets/libgl-gdi/meson.build
@@ -33,10 +33,8 @@ libopengl32 = shared_library(
   include_directories : [
     inc_common, inc_wgl, inc_gallium_winsys_sw, inc_gallium_drivers,
   ],
-  link_whole : [libwgl],
-  link_with : [
-    libgallium, libglsl, libmesa_gallium, libwsgdi, libglapi_static, libglapi
-  ],
+  link_whole : [libwgl, libgallium, libglsl, libmesa_gallium, libwsgdi, libglapi_static, libglapi],
+  link_with : [],
   dependencies : [
     dep_ws2_32, idep_nir, idep_mesautil, driver_swrast, driver_swr,
   ],
$ meson --cross .gitlab-ci/x86_64-w64-mingw32 . build/meson-windows-x86_64-debug
$ ninja -C build/meson-windows-x86_64-debug/
ninja: Entering directory `build/meson-windows-x86_64-debug/'
[2/2] Linking target src/gallium/targets/libgl-gdi/opengl32.dll.
FAILED: src/gallium/targets/libgl-gdi/opengl32.dll
x86_64-w64-mingw32-g++  -o src/gallium/targets/libgl-gdi/opengl32.dll 'src/gallium/targets/libgl-gdi/c96d1e6@@opengl32 at sha/libgl_gdi.c.obj' -Wl,--allow-shlib-undefined -shared ../../src/gallium/targets/libgl-gdi/../../state_trackers/wgl/opengl32.def -Wl,--start-group -Wl,--out-implib=src/gallium/targets/libgl-gdi/opengl32.dll.a -Wl,--whole-archive src/gallium/state_trackers/wgl/libwgl.a src/gallium/auxiliary/libgallium.a src/compiler/glsl/libglsl.a src/mesa/libmesa_gallium.a src/gallium/winsys/sw/gdi/libwsgdi.a src/mapi/glapi/libglapi_static.a -Wl,--no-whole-archive -Wl,--nxcompat -Wl,--dynamicbase -static-libgcc -static-libstdc++ src/compiler/nir/libnir.a src/compiler/libcompiler.a src/util/libmesa_util.a src/util/format/libmesa_format.a subprojects/zlib-1.2.11/libz.dll.a src/gallium/drivers/softpipe/libsoftpipe.a src/compiler/glsl/glcpp/libglcpp.a src/mesa/libmesa_common.a src/mesa/libmesa_sse41.a -lws2_32 -pthread -lm -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 -Wl,--end-group
src/mesa/libmesa_common.a(main_shaderapi.c.obj): In function `_mesa_get_shader_include_cursor':
/home/jfonseca/work/vmware/opengl/mesa/build/meson-windows-x86_64-debug/../../src/mesa/main/shaderapi.c:3185: multiple definition of `_mesa_get_shader_include_cursor'
src/compiler/glsl/glcpp/libglcpp.a(pp_standalone_scaffolding.c.obj):/home/jfonseca/work/vmware/opengl/mesa/build/meson-windows-x86_64-debug/../../src/compiler/glsl/glcpp/pp_standalone_scaffolding.c:49: first defined here
src/mesa/libmesa_common.a(main_shaderapi.c.obj): In function `_mesa_set_shader_include_cursor':
/home/jfonseca/work/vmware/opengl/mesa/build/meson-windows-x86_64-debug/../../src/mesa/main/shaderapi.c:3191: multiple definition of `_mesa_set_shader_include_cursor'
src/compiler/glsl/glcpp/libglcpp.a(pp_standalone_scaffolding.c.obj):/home/jfonseca/work/vmware/opengl/mesa/build/meson-windows-x86_64-debug/../../src/compiler/glsl/glcpp/pp_standalone_scaffolding.c:57: first defined here
src/mesa/libmesa_common.a(main_shaderapi.c.obj): In function `_mesa_lookup_shader_include':
/home/jfonseca/work/vmware/opengl/mesa/build/meson-windows-x86_64-debug/../../src/mesa/main/shaderapi.c:3404: multiple definition of `_mesa_lookup_shader_include'
src/compiler/glsl/glcpp/libglcpp.a(pp_standalone_scaffolding.c.obj):/home/jfonseca/work/vmware/opengl/mesa/build/meson-windows-x86_64-debug/../../src/compiler/glsl/glcpp/pp_standalone_scaffolding.c:41: first defined here
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

I think this is wrong.  We shouldn't be relying on carefully crafting the order of linker arguments to pick the right symbol.  There should be one and one instance of every symbol.

I suppose the pp_standalone_scaffolding module should only be used when glsl is built as a command line tool no?

Jose
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