ld.lld: error: undefined symbol: __divdi3

Question

I'm trying to link two risc-v elf files together with ld.lld , but ld.lld is giving me the following error:

ld.lld: error: undefined symbol: __divdi3

I suppose that I need to link my files with some helper functions, but after looking for it in my clang lib folder ( /usr/local/Cellar/llvm/15.0.6/lib/clang/15.0.6/lib ), but in the directory, there is only a folder for darwin, as you can see here:

.
└── darwin
    ├── libclang_rt.asan_osx_dynamic.dylib
    ├── libclang_rt.cc_kext.a
    ├── libclang_rt.fuzzer_interceptors_osx.a
[more]
    ├── libclang_rt.xray-profiling_osx.a
    └── libclang_rt.xray_osx.a

So does anyone know how should I fix this link error/get the rv64i helper functions?

Thanks!

Edit: Here are the commands that I used:

/usr/local/Cellar/llvm/15.0.6/bin/clang --target=riscv64 -march=rv64i  -fno-builtin -nostdlib -ffreestanding -Wall -Wextra -Wwrite-strings -Wstrict-prototypes -pedantic -c -o build/main.o bios/main.c
riscv64-unknown-elf-as -march=rv64i -o build/start.o src/start.S
/usr/local/Cellar/llvm/15.0.6/bin/ld.lld -T link.ld -O2 -nostdlib --oformat=binary -o output.bin build/main.o build/start.o 

Answer 1

You can get a copy of the source of the functions in libgcc here: https://github.com/gcc-mirror/gcc/tree/releases/gcc-12/libgcc/config/riscv Just copy them and place them in your source and they will compile for whatever arch your compiling for

The function __divdi3 is in the div.c file

Answer 2

__divdi3 is as a routine from the compiler supporting library. In case of gcc it is called libgcc , in case of clang it's compiler-rt . You need to have compiler-rt built from the architecture in question (RISC-V) and make it available to compiler via eg sysroot or something similar (or link explicitly).

Alternatively, just do not use 64-bit division in your program, so the call will not be generated:)