[LLVMdev] Is cross-compiling for ARM on x86 with llvm/Clang possible?

[Journeyer J. Joh]

Hello list

I think I really finally found a way to crossbuild a binary for ARM using
Clang/llvm.

This message would be a documentation for someone who may concern for the
same issue with me.

- Target : TOSHIBA AC100 / Ubuntu 12.04 (https://wiki.ubuntu.com/ARM/**
TEGRA/AC100 <https://wiki.ubuntu.com/ARM/TEGRA/AC100>)
- Host : i386 Desktop PC / Ubuntu 12.04
- Toolchain on host : sudo apt-get install gcc-arm-linux-gnueabi
- Clang/llvm compile :  http://clang.llvm.org/get_started.html
- Command string for crossbuild : ./clang -v --save-temps -ccc-host-triple
arm-linux-gnueabi --sysroot=/usr/arm-linux-gnueabi -gcc-toolchain /usr/
-Wl,-dynamic-linker,/lib/ld-linux-armhf.so.3 hello.c -o hello

During this testing I found something like a bug in Clang or llvm.
Please note the Command string for crossbuild above.
Problem occurs if "-ccc-host-triple" gets "arm-linux-gnueabihf" instead
of "arm-linux-gnueabi".
Problem is that ld is called with a incomplete or no path for libgcc,
crtbegin.o and crtend.o "-gcc-toolchain" options doesn't seem to work.
Workaroud for this problem is using a command string like below.

./clang -v --save-temps -ccc-host-triple arm-linux-gnueabihf
-mfloat-abi=hard -mfpu=vfpv3-d16 --sysroot=/usr/arm-linux-gnueabihf
-gcc-toolchain /usr/ -Wl,-dynamic-linker,/lib/ld-linux-armhf.so.3
-L/usr/lib/gcc/arm-linux-gnueabihf/4.6
-L/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../../arm-linux-gnueabihf/lib/../lib
-L/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../../arm-linux-gnueabihf/lib
-L/lib/arm-linux-gnueabihf -L/usr/lib/arm-linux-gnueabihf -L/usr/lib -L/lib
hello.c -o hello

Note all library path have to be specified. And more importantly crtend.o
and crtbegin.o have to be symbolic-linked!!
I tested with a toolchain for arm-linux-gnueabihf for this test.(sudo
apt-get install gcc-arm-linux-gnueabihf)

Thank you everyone who answered for my questions.

Journeyer J. Joh

(ps. For Sid, The final binary "hello" prints "not a dynamic executable"
when asked with "ldd". But it runs very well. ^^)


2012/6/27 Sid Manning <sidneym at codeaurora.org>

> On 06/27/12 07:24, Journeyer J. Joh wrote:
>
>> Hello,
>>
>> With your kind concern and help, I now can make a binary for ARM target.
>>
>> ./clang -v --save-temps -ccc-host-triple arm-none-linux-gnueabi
>> --sysroot=/home/hum/Documents/**Projects/arm_toolchain/arm-**
>> 2010.09/arm-none-linux-**gnueabi/libc
>> -gcc-toolchain /home/hum/Documents/Projects/**arm_toolchain/arm-2010.09
>> hello.c -o hello
>>
>> The build command is shown above.
>>
>> After that, I prepared an ARM laptop, AC100 - TOSHIBA.
>> I installed Ubuntu 12.04 in the way guided from the link below.
>>
>> https://wiki.ubuntu.com/ARM/**TEGRA/AC100<https://wiki.ubuntu.com/ARM/TEGRA/AC100>
>>
>> So I moved the final binary from host PC to AC100 and executed.
>> But the binary DIDN'T RUN.
>>
>> $./hello
>>
>> returns an error message below.
>>
>> bash: ./hello: No such file hello
>>
>>
> You could try readelf -l hello and check the INTERP header.  When I've
> seen this message usually PT_INTERP points to something that the kernel
> can't find.
>
>
>
>  I need to understand why it doesn't run on ARM laptop.
>>
>> I compiled another sample program hi.c on the ARM laptop and compared
>> both - the one cross compiled "hello" and the other self host compiled
>> "hi".
>>
>> Output message of utility "file" is almost the same except Linux
>> version, one is 2.6.16 and the other is 2.6.31. But the output of "ldd"
>> shows something meaningful.
>>
>
> This is curious based on the output from ldd below, does file report each
> as, "dynamically linked".
>
>
>
>> ldd hi
>>     libc.so.6 => /lib/arm-linux-gnueabihf/libc.**so.6 (0xb6ecf000)
>>     /lib/ld-linux-armhf.so.3 (0xb6fc3000)
>>
>> ldd hello
>>     not a dynamic executable
>>
>>
>>


-- 
----------------------------------------
Journeyer J. Joh
o o s a p r o g r a m m e r
a t
g m a i l  d o t  c o m
----------------------------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120628/d0862dc2/attachment.html>