Compiling arm32 with clang - 'No available targets are compatible with triple "armv6kz-unknown-linux-gnueabihf"'

Clang Frontend
1

After installing the arm-linux-gnueabihf toolchain of gcc and g++, I tried cross-compiling with clang.

clang-10,

clang++ --target=arm-linux-gnueabihf h.cpp -o r

Works just as expected, but

clang-14.0.6,

/home/path/to/llvm-project/bin/clang --target=arm-linux-gnueabihf hello.cpp -o r

is not,
error: unable to create target: 'No available targets are compatible with triple "armv6kz-unknown-linux-gnueabihf"'

What I tried,
clang++ --target=arm-linux-gnueabihf -stdlib=libstdc++ hello.cpp -o r

error: unable to create target: 'No available targets are compatible with triple "armv6kz-unknown-linux-gnueabihf"'
1 error generated.

Forced clang to use latest toolchain downloaded from official website: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-linux-gnueabihf.tar.xz.

clang++ --sysroot=/home/path/to/toolchain/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/bin -stdlib=libstdc++ h.cpp -o r
fatal error: 'iostream' file not found
#include<iostream>
       ^~~~~~~~~~
1 error generated.

Also tried using the linaro gcc toolchain, specifically this one - gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabihf.tar.xz

Here is the verbose output,

clang++ --target=arm-linux-gnueabihf -stdlib=libstdc++ hello.cpp -o hello --verbose

clang version 15.0.0 (https://github.com/llvm/llvm-project.git df6afee9859f982fa927dc90398e82d689f19db6)
Target: arm-unknown-linux-gnueabihf
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc-cross/arm-linux-gnueabihf/10
Selected GCC installation: /usr/lib/gcc-cross/arm-linux-gnueabihf/10
Candidate multilib: .;@m32
Selected multilib: .;@m32
 "/usr/local/bin/clang-15" -cc1 -triple armv6kz-unknown-linux-gnueabihf -emit-obj -mrelax-all --mrelax-relocations -disable-free -clear-ast-before-backend -main-file-name ex.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-cpu arm1176jzf-s -target-feature +vfp2 -target-feature +vfp2sp -target-feature -vfp3 -target-feature -vfp3d16 -target-feature -vfp3d16sp -target-feature -vfp3sp -target-feature -fp16 -target-feature -vfp4 -target-feature -vfp4d16 -target-feature -vfp4d16sp -target-feature -vfp4sp -target-feature -fp-armv8 -target-feature -fp-armv8d16 -target-feature -fp-armv8d16sp -target-feature -fp-armv8sp -target-feature -fullfp16 -target-feature +fp64 -target-feature -d32 -target-feature -neon -target-feature -sha2 -target-feature -aes -target-feature -fp16fml -target-feature +strict-align -target-abi aapcs-linux -mfloat-abi hard -Wunaligned-access -fallow-half-arguments-and-returns -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -v -fcoverage-compilation-dir=/home/usr/test -resource-dir /usr/local/lib/clang/15.0.0 -internal-isystem /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include/c++/10 -internal-isystem /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include/c++/10/arm-linux-gnueabihf -internal-isystem /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include/c++/10/backward -internal-isystem /usr/local/lib/clang/15.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -fdebug-compilation-dir=/home/usr/test -ferror-limit 19 -fno-signed-char -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/ex-bae03b.o -x c++ ex.cpp
clang -cc1 version 15.0.0 based upon LLVM 15.0.0git default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include/c++/10
 /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include/c++/10/arm-linux-gnueabihf
 /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include/c++/10/backward
 /usr/local/lib/clang/15.0.0/include
 /usr/local/include
 /usr/lib/gcc-cross/arm-linux-gnueabihf/10/../../../../arm-linux-gnueabihf/include
 /usr/include
End of search list.
error: unable to create target: 'No available targets are compatible with triple "armv6kz-unknown-linux-gnueabihf"'
1 error generated.

Just some simple instructions that can be important
I built llvm from source using this,

cmake -G Ninja -DLLVM_ENABLE_RTTI=ON -DLLVM_ENABLE_EH=ON -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="llvm;clang" ../llvm
2

I can get --target=armv6kz-unknown-linux-gnueabihf working on my machine. Not sure why that isn’t working. Using --target=arm-unknown-linux-gnueabihf will generate code for an arm7tdmi which is quite old. You can use -march=armv6kz or -mcpu=arm1176jzf-s assuming you are targeting something a first revision raspberry PI.

The sysroots from the linaro/Arm linux toolchains can confuse clang’s sysroot/toolchain detection. I’ve had the most luck with by using --sysroot in combination with --gcc-toolchain. For example: --sysroot=/path/to/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc --gcc-toolchain=/path/to/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabihf

Note that sysroot should be set to the arm-linux-gnueabihf/libc directory. If you want to run the result on qemu-arm you’ll need -L to be set to the same sysroot.

3

I am guessing that the LLVM / Clang is built with LLVM_TARGETS_TO_BUILD=Native or X86 or something so that ARM is not included.

4

I built llvm from source using this,

cmake -G Ninja -DLLVM_ENABLE_RTTI=ON -DLLVM_ENABLE_EH=ON -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="llvm;clang" ../llvm
5

You need to add ARM to the list of targets like this:

-DLLVM_TARGETS_TO_BUILD=“X86;ARM”

6

Thanks for the reply.

7

Thanks, that was the problem.