I'm building an Android tree 5.1.0_r3, that for some modules uses Clang as compiler. To avoid a reloc issue I had to apply a one-line patch that specifies to the system to use external (in-tree) assembler instead of the system one, as explained here https://stackoverflow.com/a/39638631/6350583
Now that problem is gone, but my build fails at linking.
This is the error:
art/runtime/class_linker.cc:376: error: undefined reference to 'art_quick_generic_jni_trampoline' .....
.....
clang: error: linker command failed with exit code 1 (use -v to see invocation) make: *** [out/host/linux-x86/obj32/lib/libart.so] Error 1
I omitted all the lines in the middle, because they show always the same error for different functions. Here you can find the complete output
http://pastebin.com/Q9hJ0Q7Y
You can see they're mostly art-related. Someone refers to bionic, like __memcmp16
Problems seems to be that clang is able to correctly build c++ sources but, when processing assembly .S files, it generates only almost empty object files of 516 bytes. I added the verbose flag to get the invocation line
host asm: libart_32 <= art/runtime/arch/x86/memcmp16_x86.S
clang version 3.5
Target: i386--linux-gnu
Thread model: posix
"prebuilts/clang/linux-x86/host/3.5/bin/clang" -cc1 -triple i386--linux-gnu -E -disable-free -disable-llvm-verifier -main-file-name memcmp16_x86.S -mrelocation-model pic -pic-level 2 -relaxed-aliasing -fmath-errno -masm-verbose -no-integrated-as -mconstructor-aliases -target-cpu prescott -target-feature +sse3 -target-linker-version 2.22 -momit-leaf-frame-pointer -v -g -coverage-file /tmp/memcmp16_x86-23e2cb.s -resource-dir prebuilts/clang/linux-x86/host/3.5/bin/../lib/clang/3.5 -dependency-file out/host/linux-x86/obj32/SHARED_LIBRARIES/libart_intermediates/arch/x86/memcmp16_x86.d -MT out/host/linux-x86/obj32/SHARED_LIBRARIES/libart_intermediates/arch/x86/memcmp16_x86.o -sys-header-deps -isystem system/core/include -isystem hardware/libhardware/include -isystem hardware/libhardware_legacy/include -isystem hardware/ril/include -isystem libnativehelper/include -isystem frameworks/native/include -isystem frameworks/native/opengl/include -isystem frameworks/av/include -isystem frameworks/base/include -isystem tools/include -isystem out/host/linux-x86/obj/include -isystem prebuilts/clang/linux-x86/host/3.5/lib/clang/3.5/include/ -include build/core/combo/include/arch/linux-x86/AndroidConfig.h -U _FORTIFY_SOURCE -D _FORTIFY_SOURCE=0 -D __STDC_FORMAT_MACROS -D __STDC_CONSTANT_MACROS
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D NDEBUG -U DEBUG -D __compiler_offsetof=__builtin_offsetof -D __ASSEMBLY__ -I external/libcxx/include -I external/gtest/include -I external/valgrind/main/include -I external/valgrind/main -I external/vixl/src -I external/zlib -I frameworks/compile/mclinker/include -I art/sigchainlib -I art/runtime -I out/host/linux-x86/obj32/SHARED_LIBRARIES/libart_intermediates -I out/host/linux-x86/gen/SHARED_LIBRARIES/libart_intermediates -I libnativehelper/include/nativehelper -I vendor/mediatek/proprietary/custom/y991/cgen/cfgdefault -I vendor/mediatek/proprietary/custom/y991/cgen/cfgfileinc -I vendor/mediatek/proprietary/custom/y991/cgen/inc -I vendor/mediatek/proprietary/custom/y991/cgen -I vendor/mediatek/proprietary/custom/mt6795/cgen/cfgdefault -I vendor/mediatek/proprietary/custom/mt6795/cgen/cfgfileinc -I vendor/mediatek/proprietary/custom/mt6795/cgen/inc -I vendor/mediatek/proprietary/custom/mt6795/cgen -I vendor/mediatek/proprietary/custom/common/cgen/cfgdefault -I vendor/mediatek/proprietary/custom/common/cgen/cfgfileinc -I vendor/mediatek/proprietary/custom/common/cgen/inc -I vendor/mediatek/proprietary/custom/common/cgen -isysroot prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/sysroot -internal-isystem prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/sysroot/usr/local/include -internal-isystem prebuilts/clang/linux-x86/host/3.5/bin/../lib/clang/3.5/include -internal-externc-isystem prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/sysroot/include -internal-externc-isystem prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/sysroot/usr/include -O2 -Wno-multichar -W -Wall -Wno-unused -Winit-self -Wpointer-arith -Werror=int-conversion -fno-dwarf-directory-asm -fdebug-compilation-dir /home/Ubuntu/javier/dati/download/part-tree -ferror-limit 19 -fmessage-length 0 -backend-option -force-align-stack -mstackrealign -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -dM -o /tmp/memcmp16_x86-23e2cb.s -x assembler-with-cpp art/runtime/arch/x86/memcmp16_x86.S
Here you can find the same output line-wrapped http://pastebin.com/2DFAbHuc I omitted some lines which were just a bunch of Android-specific variable definitions, to make the output easier to read.
EDIT
I found a subsequent invocation of the assembler. Still don't know where the problem resides.
"prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/x86_64-linux/bin/as" --32 --noexecstack -o out/host/linux-x86/obj32/SHARED_LIBRARIES/libart_intermediates/arch/x86/memcmp16_x86.o /tmp/memcmp16_x86-23e2cb.s
