llvm dev - Mar 2015 - [LLVMdev] Customize Standard C Library Using LLVM (to support llvm backend optimization)

2015-03-12 10:49 GMT-05:00 Jonathan Roelofs <jonathan at
codesourcery.com>:
> You need to build a sysroot from the lib and include directories in
> ~/research/musl-1.1.6 combined with the same folders from
> /usr/local/arm-2009q, then use `--sysroot` instead of the `-I`s and
`-L's.

I copied everything from the lib in musl-1.1.6
to arm-2009q3/arm-none-linux-gnueabi/libc/usr/lib but there is still an
error message:

src/env/__libc_start_main.c:(.text+0x40): undefined reference to
`__aeabi_memset'
collect2: ld returned 1 exit status

it seems that I need an arm-none-linux-gcc-4.9 (current version from
arm-2009q3 is gcc-4.4) to support  the `__aeabi_memset' function?

Regards,
Chao
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On 3/12/15 1:59 PM, Chao Yan wrote:
>
> 2015-03-12 10:49 GMT-05:00 Jonathan Roelofs <jonathan at
codesourcery.com
> <mailto:jonathan at codesourcery.com>>:
>
>     You need to build a sysroot from the lib and include directories in
>     ~/research/musl-1.1.6 combined with the same folders from
>     /usr/local/arm-2009q, then use `--sysroot` instead of the `-I`s and
>     `-L's.
>
>
> I copied everything from the lib in musl-1.1.6
> to arm-2009q3/arm-none-linux-gnueabi/libc/usr/lib but there is still an
> error message:
>
> src/env/__libc_start_main.c:(.text+0x40): undefined reference to
> `__aeabi_memset'
> collect2: ld returned 1 exit status
>
> it seems that I need an arm-none-linux-gcc-4.9 (current version from
> arm-2009q3 is gcc-4.4) to support  the `__aeabi_memset' function?
This isn't a gcc support mailing list... If you have questions 
pertaining to llvm/clang, we'd be happy to answer them.

That being said, that symbol should be part of the compiler's runtime 
library (or maybe in the libc?). llvm provides that symbol as part of 
libclangrt/libcompiler_rt.


Jon
>
> Regards,
> Chao
-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded

On 3/27/15 8:07 PM, Chao Yan wrote:
>
> 2015-03-12 15:07 GMT-05:00 Jonathan Roelofs <jonathan at
codesourcery.com
> <mailto:jonathan at codesourcery.com>>:
>
>     This isn't a gcc support mailing list... If you have questions
>     pertaining to llvm/clang, we'd be happy to answer them.
>
>     That being said, that symbol should be part of the compiler's
>     runtime library (or maybe in the libc?). llvm provides that symbol
>     as part of libclangrt/libcompiler_rt.
>
> The problem is basically caused by llvm. I cross-compile the musl-libc
> to arm binaries using clang. However, the cross-compiled musl-libc needs
> runtime support from libcompiler_rt. The arm version of this static
> runtime library cannot be obtained by cross compiling.
Where did you read that? Because it's plainly not true.

libcompiler_rt is *designed* to be cross-built, and building the ARM 
version of it from x86 Linux/Darwin is well exercised by several members 
of the community, myself included.
> Do I need to build llvm on an arm host machine?
No. LLVM/Clang is a cross compiler. Building host binaries is just a 
special, easier case of that.


Jon
>
> Thanks,
> Chao
>
-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded

2015-03-28 8:53 GMT-05:00 Jonathan Roelofs <jonathan at codesourcery.com>:
> libcompiler_rt is *designed* to be cross-built, and building the ARM
> version of it from x86 Linux/Darwin is well exercised by several members of
> the community, myself included.

Thank you for helping Jon. I'm still learning the llvm cross compiling
stuff, sometimes I might misunderstand it. I tried "make clang_linux"
in
the compiler_rt directory, it would only build the "libcompiler_rt.a"
for
x86_64, which is my host machine ISA. Could you please tell me how can I
build the arm version? I tried to modify the
"make/platform/arm_linux.mk"
and "make/options.mk", but none of them work.

Thanks,
Chao
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