[musl] Newbie cross compiling with LLVM

[musl] Newbie cross compiling with LLVM

[Matt Andrews]

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Hello everyone,

I'm trying to cross compile from Ubuntu 20.04 to armv7a-linux-musleabihf
using LLVM. Configure looks like this

./configure \
--prefix=$VECX/usr \
--syslibdir=$VECX/lib \
--target=armv7a-linux-eabihf \
CC=/usr/lib/llvm-13/bin/clang \
CFLAGS="--target=armv7a-linux-eabihf -mcpu=cortex-a8"

Then

make && make install

The compilation fails with the following

make: armv7a-linux-eabihf-ar: Command not found
make: *** [Makefile:167: lib/libc.a] Error 127

It's looking for an archiver from a cross compiler toolchain, but should be
using llvm-ar.

Which configure options should I use to get LLVM to cross compile
successfully?

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Re: [musl] Newbie cross compiling with LLVM

[Quentin Rameau]

> Hello everyone,

Hi Matt,

> I'm trying to cross compile from Ubuntu 20.04 to armv7a-linux-musleabihf
> using LLVM. Configure looks like this
> 
> ./configure \
> --prefix=$VECX/usr \
> --syslibdir=$VECX/lib \
> --target=armv7a-linux-eabihf \
> CC=/usr/lib/llvm-13/bin/clang \
> CFLAGS="--target=armv7a-linux-eabihf -mcpu=cortex-a8"
> 
> Then
> 
> make && make install
> 
> The compilation fails with the following
> 
> make: armv7a-linux-eabihf-ar: Command not found
> make: *** [Makefile:167: lib/libc.a] Error 127
> 
> It's looking for an archiver from a cross compiler toolchain, but should be
> using llvm-ar.
> 
> Which configure options should I use to get LLVM to cross compile
> successfully?

Have try with setting passing AR=clang-ar?

Re: [musl] Newbie cross compiling with LLVM

[Matt Andrews]

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> Have try with setting passing AR=clang-ar?

I actually set

    AR=/usr/lib/llvm-13/bin/llvm-ar

Then I set

    RANLIB=/usr/lib/llvm-13/bin/llvm-ranlib

That got me a little further down the road, but now I'm getting this error

    /usr/bin/ld: unrecognised emulation mode: armelf_linux_eabi
    Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu
elf_l1om elf_k1om i386pep i386pe
    clang: error: linker command failed with exit code 1 (use -v to see
invocation)

I added this to CFLAGS

    -B/usr/lib/llvm-13/bin

But it still uses the system linker.

How do I specify which linker to use?

On Mon, 11 Oct 2021 at 09:44, Quentin Rameau <quinq@fifth.space> wrote:

> > Hello everyone,
>
> Hi Matt,
>
> > I'm trying to cross compile from Ubuntu 20.04 to armv7a-linux-musleabihf
> > using LLVM. Configure looks like this
> >
> > ./configure \
> > --prefix=$VECX/usr \
> > --syslibdir=$VECX/lib \
> > --target=armv7a-linux-eabihf \
> > CC=/usr/lib/llvm-13/bin/clang \
> > CFLAGS="--target=armv7a-linux-eabihf -mcpu=cortex-a8"
> >
> > Then
> >
> > make && make install
> >
> > The compilation fails with the following
> >
> > make: armv7a-linux-eabihf-ar: Command not found
> > make: *** [Makefile:167: lib/libc.a] Error 127
> >
> > It's looking for an archiver from a cross compiler toolchain, but should
> be
> > using llvm-ar.
> >
> > Which configure options should I use to get LLVM to cross compile
> > successfully?
>
> Have try with setting passing AR=clang-ar?
>

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Re: [musl] Newbie cross compiling with LLVM

[Khem Raj]

On Sun, Oct 10, 2021 at 4:22 PM Matt Andrews <mattandrews@gmail.com> wrote:
>
> > Have try with setting passing AR=clang-ar?
>
> I actually set
>
>     AR=/usr/lib/llvm-13/bin/llvm-ar
>
> Then I set
>
>     RANLIB=/usr/lib/llvm-13/bin/llvm-ranlib
>
> That got me a little further down the road, but now I'm getting this error
>
>     /usr/bin/ld: unrecognised emulation mode: armelf_linux_eabi
>     Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu elf_l1om elf_k1om i386pep i386pe
>     clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> I added this to CFLAGS
>
>     -B/usr/lib/llvm-13/bin
>
> But it still uses the system linker.
>
> How do I specify which linker to use?

I guess you need a cross linker here if your -target option matches
exactly with cross prefix it will find it.

>
> On Mon, 11 Oct 2021 at 09:44, Quentin Rameau <quinq@fifth.space> wrote:
>>
>> > Hello everyone,
>>
>> Hi Matt,
>>
>> > I'm trying to cross compile from Ubuntu 20.04 to armv7a-linux-musleabihf
>> > using LLVM. Configure looks like this
>> >
>> > ./configure \
>> > --prefix=$VECX/usr \
>> > --syslibdir=$VECX/lib \
>> > --target=armv7a-linux-eabihf \
>> > CC=/usr/lib/llvm-13/bin/clang \
>> > CFLAGS="--target=armv7a-linux-eabihf -mcpu=cortex-a8"
>> >
>> > Then
>> >
>> > make && make install
>> >
>> > The compilation fails with the following
>> >
>> > make: armv7a-linux-eabihf-ar: Command not found
>> > make: *** [Makefile:167: lib/libc.a] Error 127
>> >
>> > It's looking for an archiver from a cross compiler toolchain, but should be
>> > using llvm-ar.
>> >
>> > Which configure options should I use to get LLVM to cross compile
>> > successfully?
>>
>> Have try with setting passing AR=clang-ar?

Re: [musl] Newbie cross compiling with LLVM

[Jeffrey Walton]

On Sun, Oct 10, 2021 at 7:22 PM Matt Andrews <mattandrews@gmail.com> wrote:
>
> > Have try with setting passing AR=clang-ar?
>
> I actually set
>
>     AR=/usr/lib/llvm-13/bin/llvm-ar
>
> Then I set
>
>     RANLIB=/usr/lib/llvm-13/bin/llvm-ranlib
>
> That got me a little further down the road, but now I'm getting this error
>
>     /usr/bin/ld: unrecognised emulation mode: armelf_linux_eabi
>     Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu elf_l1om elf_k1om i386pep i386pe
>     clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> I added this to CFLAGS
>
>     -B/usr/lib/llvm-13/bin
>
> But it still uses the system linker.

That's a linker flag. It should be added to LDFLAGS, not CFLAGS.

> How do I specify which linker to use?

LD. Also see https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html.

Typically, during a cross-compile of a C/C++ program, you set the
following variables:

* CC
* CXX
* CPP (C preprocessor)
* CPPFLAGS (this is where you put --isysroot)
* CFLAGS
* CXXFLAGS
* LD
* LDFLAGS (this is where you put --sysroot)

--isysroot tells the build system where to find the target's header
files. --sysroot tells the build system where to find the target's
libraries.

Set all the variables. Do not leave anything to chance.

If you set your variables properly and the build fails, then the
makefile or Autotool's configure.ac is broken. That happens a lot.

Jeff

Re: [musl] Newbie cross compiling with LLVM

[Matt Andrews]

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>> How do I specify which linker to use?
>
>LD. Also see
https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html.

Looking at the ./configure for musl (which is not based on autoconf
according to the docs), there is no mention of LD. Setting LD for
./configure and/or the call to make still results in the error.

Who calls the linker? The compiler or make? Shouldn't clang know where it's
linker is? How to tell clang which linker to use?

On Tue, Oct 12, 2021 at 4:41 AM Jeffrey Walton <noloader@gmail.com> wrote:

> On Sun, Oct 10, 2021 at 7:22 PM Matt Andrews <mattandrews@gmail.com>
> wrote:
> >
> > > Have try with setting passing AR=clang-ar?
> >
> > I actually set
> >
> >     AR=/usr/lib/llvm-13/bin/llvm-ar
> >
> > Then I set
> >
> >     RANLIB=/usr/lib/llvm-13/bin/llvm-ranlib
> >
> > That got me a little further down the road, but now I'm getting this
> error
> >
> >     /usr/bin/ld: unrecognised emulation mode: armelf_linux_eabi
> >     Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu
> elf_l1om elf_k1om i386pep i386pe
> >     clang: error: linker command failed with exit code 1 (use -v to see
> invocation)
> >
> > I added this to CFLAGS
> >
> >     -B/usr/lib/llvm-13/bin
> >
> > But it still uses the system linker.
>
> That's a linker flag. It should be added to LDFLAGS, not CFLAGS.
>
> > How do I specify which linker to use?
>
> LD. Also see
> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
> .
>
> Typically, during a cross-compile of a C/C++ program, you set the
> following variables:
>
> * CC
> * CXX
> * CPP (C preprocessor)
> * CPPFLAGS (this is where you put --isysroot)
> * CFLAGS
> * CXXFLAGS
> * LD
> * LDFLAGS (this is where you put --sysroot)
>
> --isysroot tells the build system where to find the target's header
> files. --sysroot tells the build system where to find the target's
> libraries.
>
> Set all the variables. Do not leave anything to chance.
>
> If you set your variables properly and the build fails, then the
> makefile or Autotool's configure.ac is broken. That happens a lot.
>
> Jeff
>

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Re: [musl] Newbie cross compiling with LLVM

[Jeffrey Walton]

On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com> wrote:
>
> >> How do I specify which linker to use?
> >
> >LD. Also see https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html.
>
> Looking at the ./configure for musl (which is not based on autoconf according to the docs), there is no mention of LD. Setting LD for ./configure and/or the call to make still results in the error.
>
> Who calls the linker? The compiler or make? Shouldn't clang know where it's linker is? How to tell clang which linker to use?

You can have the compiler driver call the linker for you by specifying
-o with an output file name. In that case, $CC or $CXX will drive the
link. And in this case, your LDFLAGS should prefix options with -Wl to
tell the compiler driver the option is for the linker.

Jeff

Re: [musl] Newbie cross compiling with LLVM

[Nagakamira]

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-fuse-ld=lld

On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com> wrote:

> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
> wrote:
> >
> > >> How do I specify which linker to use?
> > >
> > >LD. Also see
> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
> .
> >
> > Looking at the ./configure for musl (which is not based on autoconf
> according to the docs), there is no mention of LD. Setting LD for
> ./configure and/or the call to make still results in the error.
> >
> > Who calls the linker? The compiler or make? Shouldn't clang know where
> it's linker is? How to tell clang which linker to use?
>
> You can have the compiler driver call the linker for you by specifying
> -o with an output file name. In that case, $CC or $CXX will drive the
> link. And in this case, your LDFLAGS should prefix options with -Wl to
> tell the compiler driver the option is for the linker.
>
> Jeff
>

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Re: [musl] Newbie cross compiling with LLVM

[Matt Andrews]

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> -fuse-ld=lld

I actually used

    -fuse-ld=ld.lld

That did the trick, but has unlocked another error

    ld.lld: error: unable to find library -lgcc
    ld.lld: error: unable to find library -lgcc_eh

I thought musl compiles with it's own headers?

On Tue, Oct 12, 2021 at 3:54 PM Nagakamira <nagakamira@gmail.com> wrote:

> -fuse-ld=lld
>
> On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com> wrote:
>
>> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
>> wrote:
>> >
>> > >> How do I specify which linker to use?
>> > >
>> > >LD. Also see
>> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>> .
>> >
>> > Looking at the ./configure for musl (which is not based on autoconf
>> according to the docs), there is no mention of LD. Setting LD for
>> ./configure and/or the call to make still results in the error.
>> >
>> > Who calls the linker? The compiler or make? Shouldn't clang know where
>> it's linker is? How to tell clang which linker to use?
>>
>> You can have the compiler driver call the linker for you by specifying
>> -o with an output file name. In that case, $CC or $CXX will drive the
>> link. And in this case, your LDFLAGS should prefix options with -Wl to
>> tell the compiler driver the option is for the linker.
>>
>> Jeff
>>
>

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Re: [musl] Newbie cross compiling with LLVM

[Nagakamira]

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--rtlib=compiler-rt

On Tue, Oct 12, 2021, 7:58 AM Matt Andrews <mattandrews@gmail.com> wrote:

> > -fuse-ld=lld
>
> I actually used
>
>     -fuse-ld=ld.lld
>
> That did the trick, but has unlocked another error
>
>     ld.lld: error: unable to find library -lgcc
>     ld.lld: error: unable to find library -lgcc_eh
>
> I thought musl compiles with it's own headers?
>
> On Tue, Oct 12, 2021 at 3:54 PM Nagakamira <nagakamira@gmail.com> wrote:
>
>> -fuse-ld=lld
>>
>> On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com> wrote:
>>
>>> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
>>> wrote:
>>> >
>>> > >> How do I specify which linker to use?
>>> > >
>>> > >LD. Also see
>>> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>>> .
>>> >
>>> > Looking at the ./configure for musl (which is not based on autoconf
>>> according to the docs), there is no mention of LD. Setting LD for
>>> ./configure and/or the call to make still results in the error.
>>> >
>>> > Who calls the linker? The compiler or make? Shouldn't clang know where
>>> it's linker is? How to tell clang which linker to use?
>>>
>>> You can have the compiler driver call the linker for you by specifying
>>> -o with an output file name. In that case, $CC or $CXX will drive the
>>> link. And in this case, your LDFLAGS should prefix options with -Wl to
>>> tell the compiler driver the option is for the linker.
>>>
>>> Jeff
>>>
>>

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Re: [musl] Newbie cross compiling with LLVM

[Matt Andrews]

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> --rtlib=compiler-rt

Is that a compiler option or a linker option? I used it in both places, but
still get the same error.

On Tue, Oct 12, 2021 at 4:00 PM Nagakamira <nagakamira@gmail.com> wrote:

> --rtlib=compiler-rt
>
> On Tue, Oct 12, 2021, 7:58 AM Matt Andrews <mattandrews@gmail.com> wrote:
>
>> > -fuse-ld=lld
>>
>> I actually used
>>
>>     -fuse-ld=ld.lld
>>
>> That did the trick, but has unlocked another error
>>
>>     ld.lld: error: unable to find library -lgcc
>>     ld.lld: error: unable to find library -lgcc_eh
>>
>> I thought musl compiles with it's own headers?
>>
>> On Tue, Oct 12, 2021 at 3:54 PM Nagakamira <nagakamira@gmail.com> wrote:
>>
>>> -fuse-ld=lld
>>>
>>> On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com> wrote:
>>>
>>>> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
>>>> wrote:
>>>> >
>>>> > >> How do I specify which linker to use?
>>>> > >
>>>> > >LD. Also see
>>>> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>>>> .
>>>> >
>>>> > Looking at the ./configure for musl (which is not based on autoconf
>>>> according to the docs), there is no mention of LD. Setting LD for
>>>> ./configure and/or the call to make still results in the error.
>>>> >
>>>> > Who calls the linker? The compiler or make? Shouldn't clang know
>>>> where it's linker is? How to tell clang which linker to use?
>>>>
>>>> You can have the compiler driver call the linker for you by specifying
>>>> -o with an output file name. In that case, $CC or $CXX will drive the
>>>> link. And in this case, your LDFLAGS should prefix options with -Wl to
>>>> tell the compiler driver the option is for the linker.
>>>>
>>>> Jeff
>>>>
>>>

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Re: [musl] Newbie cross compiling with LLVM

[Nagakamira]

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You can pass --unwindlib=libunwind and rtlib, they are both link options

On Tue, Oct 12, 2021, 8:55 AM Matt Andrews <mattandrews@gmail.com> wrote:

> > --rtlib=compiler-rt
>
> Is that a compiler option or a linker option? I used it in both places,
> but still get the same error.
>
> On Tue, Oct 12, 2021 at 4:00 PM Nagakamira <nagakamira@gmail.com> wrote:
>
>> --rtlib=compiler-rt
>>
>> On Tue, Oct 12, 2021, 7:58 AM Matt Andrews <mattandrews@gmail.com> wrote:
>>
>>> > -fuse-ld=lld
>>>
>>> I actually used
>>>
>>>     -fuse-ld=ld.lld
>>>
>>> That did the trick, but has unlocked another error
>>>
>>>     ld.lld: error: unable to find library -lgcc
>>>     ld.lld: error: unable to find library -lgcc_eh
>>>
>>> I thought musl compiles with it's own headers?
>>>
>>> On Tue, Oct 12, 2021 at 3:54 PM Nagakamira <nagakamira@gmail.com> wrote:
>>>
>>>> -fuse-ld=lld
>>>>
>>>> On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com>
>>>> wrote:
>>>>
>>>>> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
>>>>> wrote:
>>>>> >
>>>>> > >> How do I specify which linker to use?
>>>>> > >
>>>>> > >LD. Also see
>>>>> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>>>>> .
>>>>> >
>>>>> > Looking at the ./configure for musl (which is not based on autoconf
>>>>> according to the docs), there is no mention of LD. Setting LD for
>>>>> ./configure and/or the call to make still results in the error.
>>>>> >
>>>>> > Who calls the linker? The compiler or make? Shouldn't clang know
>>>>> where it's linker is? How to tell clang which linker to use?
>>>>>
>>>>> You can have the compiler driver call the linker for you by specifying
>>>>> -o with an output file name. In that case, $CC or $CXX will drive the
>>>>> link. And in this case, your LDFLAGS should prefix options with -Wl to
>>>>> tell the compiler driver the option is for the linker.
>>>>>
>>>>> Jeff
>>>>>
>>>>

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Re: [musl] Newbie cross compiling with LLVM

[Matt Andrews]

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I'm currently using this to compile with LLVM

AR=/usr/lib/llvm-13/bin/llvm-ar \
RANLIB=/usr/lib/llvm-13/bin/llvm-ranlib \
CC=/usr/lib/llvm-13/bin/clang \
CFLAGS="-fuse-ld=/usr/lib/llvm-13/bin/ld.lld --rtlib=compiler-rt
--target=armv7a-linux-eabihf -mcpu=cortex-a8" \
LIBCC=-lcompiler_rt \
./configure \
--prefix=$PREFIX/usr \
--syslibdir=$PREFIX/lib \
--target=armv7a-linux-eabihf \
&& make \
&& make install

This is the output from ./configure

checking for C compiler... /usr/lib/llvm-13/bin/clang
checking whether C compiler works... yes
checking whether compiler accepts -Werror=unknown-warning-option... yes
checking whether compiler accepts -Werror=unused-command-line-argument...
yes
checking whether compiler accepts -Werror=ignored-optimization-argument...
yes
checking whether linker accepts -Werror=unknown-warning-option... yes
checking whether linker accepts -Werror=unused-command-line-argument... yes
checking for C compiler family... clang
checking for toolchain wrapper to build... clang
checking target system type... armv7a-linux-eabihf
checking whether compiler accepts -std=c99... yes
checking whether compiler accepts -nostdinc... yes
checking whether compiler accepts -ffreestanding... yes
checking whether compiler accepts -fexcess-precision=standard... no
checking whether compiler accepts -frounding-math... yes
checking whether compiler needs attribute((may_alias)) suppression... no
checking whether compiler accepts -Wa,--noexecstack... yes
checking whether compiler accepts -fno-stack-protector... yes
checking whether compiler accepts -fno-tree-loop-distribute-patterns... no
checking whether we should preprocess assembly to add debugging
information... no
checking for optimization settings... using defaults
checking whether compiler accepts -Os... yes
components to be optimized for speed: internal malloc string
checking whether compiler accepts -pipe... yes
checking whether compiler accepts -fomit-frame-pointer... yes
checking whether compiler accepts -fno-unwind-tables... yes
checking whether compiler accepts -fno-asynchronous-unwind-tables... yes
checking whether compiler accepts -ffunction-sections... yes
checking whether compiler accepts -fdata-sections... yes
checking whether compiler accepts -w... yes
checking whether compiler accepts -Wno-pointer-to-int-cast... yes
checking whether compiler accepts -Werror=implicit-function-declaration...
yes
checking whether compiler accepts -Werror=implicit-int... yes
checking whether compiler accepts -Werror=pointer-sign... yes
checking whether compiler accepts -Werror=pointer-arith... yes
checking whether compiler accepts -Werror=int-conversion... yes
checking whether compiler accepts -Werror=incompatible-pointer-types... yes
checking whether compiler accepts -Werror=discarded-qualifiers... no
checking whether compiler accepts -Werror=discarded-array-qualifiers... no
checking whether compiler accepts -Qunused-arguments... yes
checking whether compiler accepts -Waddress... yes
checking whether compiler accepts -Warray-bounds... yes
checking whether compiler accepts -Wchar-subscripts... yes
checking whether compiler accepts -Wduplicate-decl-specifier... yes
checking whether compiler accepts -Winit-self... yes
checking whether compiler accepts -Wreturn-type... yes
checking whether compiler accepts -Wsequence-point... yes
checking whether compiler accepts -Wstrict-aliasing... yes
checking whether compiler accepts -Wunused-function... yes
checking whether compiler accepts -Wunused-label... yes
checking whether compiler accepts -Wunused-variable... yes
checking preprocessor condition __PIC__... false
checking whether linker accepts -Wl,--sort-section,alignment... yes
checking whether linker accepts -Wl,--sort-common... yes
checking whether linker accepts -Wl,--gc-sections... yes
checking whether linker accepts -Wl,--hash-style=both... yes
checking whether linker accepts -Wl,--no-undefined... yes
checking whether linker accepts -Wl,--exclude-libs=ALL... yes
checking whether linker accepts -Wl,--dynamic-list=./dynamic.list... yes
using compiler runtime libraries: -lcompiler_rt
checking preprocessor condition __thumb2__... false
checking preprocessor condition __ARMEB__... false
checking preprocessor condition __ARM_PCS_VFP... true
checking whether clang's vfp asm constraints work... yes
configured for arm variant: armhf
checking whether compiler's long double definition matches float.h... yes
checking preprocessor condition __FAST_MATH__... false
creating config.mak... done

but now I get this error when compiling

ld.lld: error: unable to find library -lcompiler_rt

Have I made an error in the way I'm calling ./configure?

Just to reiterate, I'm trying to use LLVM to cross compile from x86_64
Linux to armv7a-linux-eabihf.

On Tue, Oct 12, 2021 at 5:09 PM Nagakamira <nagakamira@gmail.com> wrote:

> You can pass --unwindlib=libunwind and rtlib, they are both link options
>
> On Tue, Oct 12, 2021, 8:55 AM Matt Andrews <mattandrews@gmail.com> wrote:
>
>> > --rtlib=compiler-rt
>>
>> Is that a compiler option or a linker option? I used it in both places,
>> but still get the same error.
>>
>> On Tue, Oct 12, 2021 at 4:00 PM Nagakamira <nagakamira@gmail.com> wrote:
>>
>>> --rtlib=compiler-rt
>>>
>>> On Tue, Oct 12, 2021, 7:58 AM Matt Andrews <mattandrews@gmail.com>
>>> wrote:
>>>
>>>> > -fuse-ld=lld
>>>>
>>>> I actually used
>>>>
>>>>     -fuse-ld=ld.lld
>>>>
>>>> That did the trick, but has unlocked another error
>>>>
>>>>     ld.lld: error: unable to find library -lgcc
>>>>     ld.lld: error: unable to find library -lgcc_eh
>>>>
>>>> I thought musl compiles with it's own headers?
>>>>
>>>> On Tue, Oct 12, 2021 at 3:54 PM Nagakamira <nagakamira@gmail.com>
>>>> wrote:
>>>>
>>>>> -fuse-ld=lld
>>>>>
>>>>> On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
>>>>>> wrote:
>>>>>> >
>>>>>> > >> How do I specify which linker to use?
>>>>>> > >
>>>>>> > >LD. Also see
>>>>>> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>>>>>> .
>>>>>> >
>>>>>> > Looking at the ./configure for musl (which is not based on autoconf
>>>>>> according to the docs), there is no mention of LD. Setting LD for
>>>>>> ./configure and/or the call to make still results in the error.
>>>>>> >
>>>>>> > Who calls the linker? The compiler or make? Shouldn't clang know
>>>>>> where it's linker is? How to tell clang which linker to use?
>>>>>>
>>>>>> You can have the compiler driver call the linker for you by specifying
>>>>>> -o with an output file name. In that case, $CC or $CXX will drive the
>>>>>> link. And in this case, your LDFLAGS should prefix options with -Wl to
>>>>>> tell the compiler driver the option is for the linker.
>>>>>>
>>>>>> Jeff
>>>>>>
>>>>>

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Re: [musl] Newbie cross compiling with LLVM

[Nagakamira]

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you need to compile compiler-rt builtins and put them in clang folder and
then pass LIBCC="$(clang --target=blah-blah-blah -print-libgcc-file-name)"

On Tue, Oct 12, 2021 at 7:34 PM Matt Andrews <mattandrews@gmail.com> wrote:

> I'm currently using this to compile with LLVM
>
> AR=/usr/lib/llvm-13/bin/llvm-ar \
> RANLIB=/usr/lib/llvm-13/bin/llvm-ranlib \
> CC=/usr/lib/llvm-13/bin/clang \
> CFLAGS="-fuse-ld=/usr/lib/llvm-13/bin/ld.lld --rtlib=compiler-rt
> --target=armv7a-linux-eabihf -mcpu=cortex-a8" \
> LIBCC=-lcompiler_rt \
> ./configure \
> --prefix=$PREFIX/usr \
> --syslibdir=$PREFIX/lib \
> --target=armv7a-linux-eabihf \
> && make \
> && make install
>
> This is the output from ./configure
>
> checking for C compiler... /usr/lib/llvm-13/bin/clang
> checking whether C compiler works... yes
> checking whether compiler accepts -Werror=unknown-warning-option... yes
> checking whether compiler accepts -Werror=unused-command-line-argument...
> yes
> checking whether compiler accepts -Werror=ignored-optimization-argument...
> yes
> checking whether linker accepts -Werror=unknown-warning-option... yes
> checking whether linker accepts -Werror=unused-command-line-argument... yes
> checking for C compiler family... clang
> checking for toolchain wrapper to build... clang
> checking target system type... armv7a-linux-eabihf
> checking whether compiler accepts -std=c99... yes
> checking whether compiler accepts -nostdinc... yes
> checking whether compiler accepts -ffreestanding... yes
> checking whether compiler accepts -fexcess-precision=standard... no
> checking whether compiler accepts -frounding-math... yes
> checking whether compiler needs attribute((may_alias)) suppression... no
> checking whether compiler accepts -Wa,--noexecstack... yes
> checking whether compiler accepts -fno-stack-protector... yes
> checking whether compiler accepts -fno-tree-loop-distribute-patterns... no
> checking whether we should preprocess assembly to add debugging
> information... no
> checking for optimization settings... using defaults
> checking whether compiler accepts -Os... yes
> components to be optimized for speed: internal malloc string
> checking whether compiler accepts -pipe... yes
> checking whether compiler accepts -fomit-frame-pointer... yes
> checking whether compiler accepts -fno-unwind-tables... yes
> checking whether compiler accepts -fno-asynchronous-unwind-tables... yes
> checking whether compiler accepts -ffunction-sections... yes
> checking whether compiler accepts -fdata-sections... yes
> checking whether compiler accepts -w... yes
> checking whether compiler accepts -Wno-pointer-to-int-cast... yes
> checking whether compiler accepts -Werror=implicit-function-declaration...
> yes
> checking whether compiler accepts -Werror=implicit-int... yes
> checking whether compiler accepts -Werror=pointer-sign... yes
> checking whether compiler accepts -Werror=pointer-arith... yes
> checking whether compiler accepts -Werror=int-conversion... yes
> checking whether compiler accepts -Werror=incompatible-pointer-types... yes
> checking whether compiler accepts -Werror=discarded-qualifiers... no
> checking whether compiler accepts -Werror=discarded-array-qualifiers... no
> checking whether compiler accepts -Qunused-arguments... yes
> checking whether compiler accepts -Waddress... yes
> checking whether compiler accepts -Warray-bounds... yes
> checking whether compiler accepts -Wchar-subscripts... yes
> checking whether compiler accepts -Wduplicate-decl-specifier... yes
> checking whether compiler accepts -Winit-self... yes
> checking whether compiler accepts -Wreturn-type... yes
> checking whether compiler accepts -Wsequence-point... yes
> checking whether compiler accepts -Wstrict-aliasing... yes
> checking whether compiler accepts -Wunused-function... yes
> checking whether compiler accepts -Wunused-label... yes
> checking whether compiler accepts -Wunused-variable... yes
> checking preprocessor condition __PIC__... false
> checking whether linker accepts -Wl,--sort-section,alignment... yes
> checking whether linker accepts -Wl,--sort-common... yes
> checking whether linker accepts -Wl,--gc-sections... yes
> checking whether linker accepts -Wl,--hash-style=both... yes
> checking whether linker accepts -Wl,--no-undefined... yes
> checking whether linker accepts -Wl,--exclude-libs=ALL... yes
> checking whether linker accepts -Wl,--dynamic-list=./dynamic.list... yes
> using compiler runtime libraries: -lcompiler_rt
> checking preprocessor condition __thumb2__... false
> checking preprocessor condition __ARMEB__... false
> checking preprocessor condition __ARM_PCS_VFP... true
> checking whether clang's vfp asm constraints work... yes
> configured for arm variant: armhf
> checking whether compiler's long double definition matches float.h... yes
> checking preprocessor condition __FAST_MATH__... false
> creating config.mak... done
>
> but now I get this error when compiling
>
> ld.lld: error: unable to find library -lcompiler_rt
>
> Have I made an error in the way I'm calling ./configure?
>
> Just to reiterate, I'm trying to use LLVM to cross compile from x86_64
> Linux to armv7a-linux-eabihf.
>
> On Tue, Oct 12, 2021 at 5:09 PM Nagakamira <nagakamira@gmail.com> wrote:
>
>> You can pass --unwindlib=libunwind and rtlib, they are both link options
>>
>> On Tue, Oct 12, 2021, 8:55 AM Matt Andrews <mattandrews@gmail.com> wrote:
>>
>>> > --rtlib=compiler-rt
>>>
>>> Is that a compiler option or a linker option? I used it in both places,
>>> but still get the same error.
>>>
>>> On Tue, Oct 12, 2021 at 4:00 PM Nagakamira <nagakamira@gmail.com> wrote:
>>>
>>>> --rtlib=compiler-rt
>>>>
>>>> On Tue, Oct 12, 2021, 7:58 AM Matt Andrews <mattandrews@gmail.com>
>>>> wrote:
>>>>
>>>>> > -fuse-ld=lld
>>>>>
>>>>> I actually used
>>>>>
>>>>>     -fuse-ld=ld.lld
>>>>>
>>>>> That did the trick, but has unlocked another error
>>>>>
>>>>>     ld.lld: error: unable to find library -lgcc
>>>>>     ld.lld: error: unable to find library -lgcc_eh
>>>>>
>>>>> I thought musl compiles with it's own headers?
>>>>>
>>>>> On Tue, Oct 12, 2021 at 3:54 PM Nagakamira <nagakamira@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> -fuse-ld=lld
>>>>>>
>>>>>> On Tue, Oct 12, 2021, 3:26 AM Jeffrey Walton <noloader@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> On Mon, Oct 11, 2021 at 7:55 PM Matt Andrews <mattandrews@gmail.com>
>>>>>>> wrote:
>>>>>>> >
>>>>>>> > >> How do I specify which linker to use?
>>>>>>> > >
>>>>>>> > >LD. Also see
>>>>>>> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>>>>>>> .
>>>>>>> >
>>>>>>> > Looking at the ./configure for musl (which is not based on
>>>>>>> autoconf according to the docs), there is no mention of LD. Setting LD for
>>>>>>> ./configure and/or the call to make still results in the error.
>>>>>>> >
>>>>>>> > Who calls the linker? The compiler or make? Shouldn't clang know
>>>>>>> where it's linker is? How to tell clang which linker to use?
>>>>>>>
>>>>>>> You can have the compiler driver call the linker for you by
>>>>>>> specifying
>>>>>>> -o with an output file name. In that case, $CC or $CXX will drive the
>>>>>>> link. And in this case, your LDFLAGS should prefix options with -Wl
>>>>>>> to
>>>>>>> tell the compiler driver the option is for the linker.
>>>>>>>
>>>>>>> Jeff
>>>>>>>
>>>>>>

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