Re: Yocto development with C++11 threads and gcc

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Thu, 2014-08-14 at 04:15 -0500, Peter A. Bigot wrote:
> What this means is that the libraries built by gcc-runtime use 
> TARGET_CC_ARCH settings that don't necessarily match the target 
> compiler's defaults, and that ABI conflicts can result by linking in 
> those libraries when the non-default settings were absent in non-OE 
> application builds.  ABI can only be "guaranteed" if every one of the 
> -mFOO=BAR passed in TARGET_CC_ARCH (*or defaulted by the compiler*) has 
> a corresponding -with-FOO=BAR option passed to (*or inferred by*) gcc's 
> configure.
> 
> That's a pretty strong assumption to make.
> 
> It may be that this can be worked around for the specific case I raised 
> by explicitly adding --with-arch=armv7-a to gcc-target's EXTRA_OECONF. I 
> do have to wonder whether the same should be done for any of armv7 
> armv7-m armv7-r armv7e-m armv7ve armv8-a armv8-a+crc which are other 
> -march options that are armv6+, and whether there are other ABI issues 
> that might be hiding now or in the future because TARGET_CC_ARCH makes 
> more assumptions than gcc-target does.
> 
> The solution I propose is to rework gcc-runtime's override of CC/CXX/CPP 
> so the libraries are built the same way they would be if they had been 
> built during gcc-target.
> 
>  From initial attempts this won't be easy to do.  I'd be happy to keep 
> trying if this worries other people, but if I'm being too picky I'll 
> just suck it up and move on.

Its a valid concern, I just don't think anyone else has run into the
kinds of issues you're seeing :/. We don't want to diverge too far from
upstream gcc, equally, we need a working compiler...

Cheers,

Richard