[llvm-dev] Trying to create a pure LLVM toolchain on musl based distribution

[David Demelier via llvm-dev]

Le 25/03/2019 à 14:41, Peter Smith a écrit :
> Hello David,
> 
> I don't know much about the specifics of Musl, so I'm responding generally.
> 
> As I understand it, clang expects to find the compiler-rt libraries
> relative to the resource directory, which you can find out the
> location of with clang --print-resource-dir . By default it is
> lib/clang/9.0.0 assuming you are building from master. I think that
> -DCMAKE_INSTALL_PREFIX=/usr has broken that assumption. I think that
> you would either need to take out the CMAKE_INSTALL_PREFIX or change
> the location of the resource directory, which I think that you can
> alter at build time.
> 

You're right, I've just checked both packages in Alpine and Arch and 
they indeed move the /usr/lib/linux directory under the clang's one. 
I've fixed that it worked, now I still have to find the solution 
regarding crtbeginS.so and crtendS.so.

Thanks :)

> I don't think that there is a way of preventing clang adding
> crtbeginS.o and crtendS.o without --nostdlib or --nostartfiles but
> using these options will also not add the other crt*.o files that you
> may be expecting.
> 
> There is a line in lib/Driver/Toolchains/Gnu.cpp which the Linux driver uses:
> const bool HasCRTBeginEndFiles =
>        ToolChain.getTriple().hasEnvironment() ||
>        (ToolChain.getTriple().getVendor() != llvm::Triple::MipsTechnologies);
> It looks like Musl may need to be included there?

I'll have a look, I don't know much the lowest part of the toolchain 
build process so I don't understand very much what's going on there. 
Hopefully someone that has better low-level knowledges and use musl will 
be able to guide me for this.

What can I tell is that musl provide those files:

usr/lib/Scrt1.o
usr/lib/crt1.o
usr/lib/crti.o
usr/lib/crtn.o
usr/lib/ld-musl-x86_64.so.1

Regards,

-- 
David