Re: gcc reports sysroot is /not/exist!

[Chris Simmonds <chris@2net.co.uk>]

Hi Richard,

On 15/09/15 10:45, Richard Purdie wrote:
> On Tue, 2015-09-15 at 10:20 +0100, Chris Simmonds wrote:
>>
>> Also, I am not convinced this is a step in the right direction. I expect
>> to be able to compile a simple program using:
>>
>> $ gcc hello.c -o hello
>>
>> But with this new cross compiler setup, this happens:
>>
>> $ arm-poky-linux-gnueabi-gcc hello.c -o hello
>> hello.c:1:19: fatal error: stdio.h: No such file or directory
>>  #include <stdio.h>
>>                    ^
>> compilation terminated.
> 
> If we hardcode the path to the sysroot into the compiler, we hit several
> issues. Firstly, we rely on the relocation code within gcc to get this
> relocated correctly at install time. That doesn't work for the way we
> currently build the compilers so the default sysroot only works for the
> default installation directory. Yes, that one is fixable with some
> jumping through hoops.
> 
> However if you don't want to set CFLAGS either, that implies we'd have
> to code the flags into the compiler as well. 
> 
> So we'd build a compiler per target sysroot and per set of optimisation
> flags for said target. That is grossly inefficient.

I'll admit that is the model I had in mind. However, I can see that it
does not scale well if you are addressing a range of targets as Yocto
allows you to do. So it looks like it is time for me to update my modus
operandi to match. However, I'll bet that I am not the only one caught out.

> We've always had the environment file there and we've always set CFLAGS
> this way, even in 1.7. If you used a non-default installation directory
> in 1.7, it likely didn't work properly without passing the right flags
> to gcc so you just go lucky even there. In 1.8, we poisoned the default
> sysroot, so we could clearly identify any software which wasn't using
> the CC and CFLAGS in ways we didn't expect. We did this to make our core
> builds deterministic. We decided to do the same with the SDK.
> 
> If you really object to having to configure the compiler, I'd suggest
> creating some simple wrapper scripts which simply add in the sysroot and
> possibly other compiler flag options you need. The main reason we
> accepted doing the change to the defaults is that there is a
> comparatively simple workaround available for those that feel as you
> do. 
> 
> We could even have that code in the main repo, I've just felt so far
> that letting people see whats going on is better than hiding it behind
> more magic scripts.
> 

No, I have no desire to write wrappers, I just wanted to clarify "the
right way to do things". Thank you very much for explaining it.

Chris.