Configuring newlib for cross-compilation with clang

[Vlad Ivanov]

For anyone stumbling upon this, the problem was caused by wrong options. Instead 
of CC and CFLAGS, one must use CC_FOR_TARGET and CFLAGS_FOR_TARGET.

One thing I noticed is that newlib is largely gcc-centric, and while it seems it can be 
built with clang for some targets, that is not the case with powerpc.

03.11.2020, 14:08, "Vlad Ivanov" <vlad@ivanov.email>:
> Hello,
>
> I'm trying to build newlib for a PowerPC embedded target to assemble a complete
> toolchain with clang. I need to use clang as a cross compiler; clang and llvm
> are the only tools available. The resulting toolchain targets bare metal
> environment.
>
> Here's the command I'm using:
>
> ../newlib-cygwin/configure \
>     --prefix=/opt/newlib-powerpc/install \
>     --disable-libstdcxx \
>     --disable-shared \
>     --enable-static \
>     --disable-multilib \
>     --target=powerpc-none-eabi \
>     --disable-newlib-supplied-syscalls \
>     --enable-newlib-nano-malloc \
>     --enable-target-optspace \
>     --disable-newlib-multithread \
>     --disable-newlib-io-float \
>     --enable-lite-exit \
>      CC='/usr/bin/clang'
>      CFLAGS='--target=powerpc-none-eabi'
>
> I see an error early during configuration:
>
> checking for C compiler default output file name...
> configure: error: in `/opt/newlib-powerpc/build':
> configure: error: C compiler cannot create executables
> See `config.log' for more details.
>
> Now, this error occurs because the configure script tries to compile an
> executable and it's expecting to see something like a.out. But for an
> embedded target, to link an executable, one needs a linker scripts to define
> the memory layout, since there's no OS loading the binary. So any tests
> that create executables will fail.
>
> Is it possible to tell newlib to not compile any executables? Or should I
> use something like a dummy linker script?
>
> Best Regards,
>
> Vlad