[RFC] Do we care about binary compatibility of code produced by cross-compilers?

[Paolo Carlini]

-- Ian,
> For example, while I don't know offhand whether this affects binary
> compatibility, it is incorrect to not test GCC_CHECK_TLS when being
> built by a cross-compiler.  It's true that you can't get a complete
> TLS test when being built by a cross-compiler, because you can't test
> the kernel.  However, GCC_CHECK_TLS has a reasonable fallback for that
> case: if the compiler and the binutils support TLS, it assumes that
> TLS is fully supported.  GCC_CHECK_TLS should be invoked
> unconditionally, not only if GLIBCXX_IS_NATIVE.  The same is true of
> many other--though not necessarily all--tests currently controlled by
> GLIBCXX_IS_NATIVE.
>   
I tried to make some progress in mainline, please have a look again.

As regards GCC_CHECK_TLS, at the moment I don't understand the test well 
enough to take an immediate action: in general I moved to unconditional 
testing (e.g., both native and crosses) either tests using only 
AC_TRY_COMPILE, or using GCC_TRY_COMPILE_OR_LINK, or linking only in 
non-default cases, controlled by a configure-time switch.

I don't think GCC_CHECK_TLS belongs to one of those "straightforward" 
cases, or, in other terms, I cannot convince myself that it's safe to 
move it as-is. Can you further help with it?

Thanks,
Paolo.