llvm dev - Jan 2020 - Building LLVM so it does not need gcc libraries anymore

I am trying to bootstrap LLVM with LLVM so it does not depend on gcc
libraries anymore, but I had little success. Is it possible to do it? If
yes, what am I doing wrong?

I download the llvm-8.0.1 tar.gz and build these llvm projects:
llmv;libcxx;libcxxabi;clang;clang-tools-extra;compiler-rt;libunwind

I do two round of building: a bootstrap round, and a final round.

In the bootstrap round, I build llvm with clang-8 (downloaded form llvm
apt-repo for ubuntu). I link with lld and I set -I, and -L to /include and
/lib paths. I also set the rpath.

In the final round, I copy the llvm binaries from the last round to a new
and pristine system with nothing but the llvm source code on it (to make
sure I do not depend on gcc libraries). Here I try to build the source
code, one more time, with the binaries form the bootstrap round. But my
bootstrap compiler, among other things, depends on -lgcc, and -lgcc_s. I am
wondering if it is possible to build llvm/clang so it does not depend on
them. I fiddled with multiple flags and options, including -nostdinc,
-nostdinc++, -stdlib=libc++, etc, but with no success.

Thanks,
Meisam
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Hello,

libgcc is the compiler runtime builtins. This defaults to gnu/gcc on linux.
You need to build compiler-rt builtins and crt in your first pass and then
pass --rtlib=compiler-rt in your flags (or maybe there is a
LLVM_USE_COMPILER_RT cmake variable but I can't check currently).

Hopefully this points you in the right direction.

-- Tobias

On Mon, Jan 6, 2020, 21:01 Meisam Fathi via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I am trying to bootstrap LLVM with LLVM so it does not depend on gcc
> libraries anymore, but I had little success. Is it possible to do it? If
> yes, what am I doing wrong?
>
> I download the llvm-8.0.1 tar.gz and build these llvm projects:
> llmv;libcxx;libcxxabi;clang;clang-tools-extra;compiler-rt;libunwind
>
> I do two round of building: a bootstrap round, and a final round.
>
> In the bootstrap round, I build llvm with clang-8 (downloaded form llvm
> apt-repo for ubuntu). I link with lld and I set -I, and -L to /include and
> /lib paths. I also set the rpath.
>
> In the final round, I copy the llvm binaries from the last round to a new
> and pristine system with nothing but the llvm source code on it (to make
> sure I do not depend on gcc libraries). Here I try to build the source
> code, one more time, with the binaries form the bootstrap round. But my
> bootstrap compiler, among other things, depends on -lgcc, and -lgcc_s. I am
> wondering if it is possible to build llvm/clang so it does not depend on
> them. I fiddled with multiple flags and options, including -nostdinc,
> -nostdinc++, -stdlib=libc++, etc, but with no success.
>
> Thanks,
> Meisam
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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