[yocto] Problem finding -lgcc when using SDK toolchain

[Hans Beckerus]

On 2013-10-01 7:35, Khem Raj wrote:
> On Oct 1, 2013, at 6:16 AM, Hans Beckérus <hans.beckerus at gmail.com> wrote:
>
>> Hello. We have stumbled into a problem when using ld directly instead
>> of going through the gcc frontend.
>> A simple operation like this fails:
>>
>>> ${CC} -c hello_world.c
>>> ${LD} hello_world.o -lgcc
>> arm-poky-linux-gnueabi-ld: cannot find -lgcc
>>
>> And yes, I know -lgcc is not required in this case to compile this
>> one, but this is only a simple reproducer.
>> The real issue was discovered when trying to build U-Boot from the SDK.
>>
>> To resolve this problem we are forced to provide
>> -L<sysroot>/usr/lib/arm-poky-linux-gnueabi/4.7.2 to LDFLAGS.
>> But that should not be needed, should it? Anyone else bumped into this
>> problem? Are there any "real" solutions.
>> I am starting to think it has to do with the hardcoded installation
>> path in the binaries maybe?
> I doubt that infact we try hard to keep it relocatable. The problem is you are interpreting
> --sysroot option to do more than what its supposed to do. when linking it only affects INPUT,  GROUP
> and SEARCH_DIR linker script variables and if you look at the linker script path to libgcc is not
> specified in SEARCH_DIR, thats where gcc driver comes handy in figuring out where the right libgcc is installed
> and sometimes when you have complex multilib environments thats very handy. linker does not know
> anything about libgcc its just another library for it.
Hi Khem, thanks for your time. I am sure I put too much value into --sysroot, but what still strikes me a bit odd is why the simple reproducer I showed before works just fine using the local host gcc and ld? It seems to have no issues in finding libgcc.a?
So what you are saying is that it is actually expected that U-Boot build will fail when compiled through the SDK toolchain directly without adding additional options to the linker? Is that also what the u-boot recipe is doing? After all, it works fine to bitbake u-boot.

> however you could do  something like
>
> ${CC} -print-libgcc-file-name or ${CC} -print-file-name=libgcc.a
>
> to get to the library
>
> and specify that in your linker cmdline
Ok, guess it will simply give me the same path as we are currently hardcoding, but if the toolchain moves your solution is definitely to prefer.
Thanks for the tip. Did only not know about the --print-sysroot command until now.
> -Khem