Re: Portable inline asm to get address of TLS variable

[Paolo Bonzini <pbonzini@redhat.com>]

On 2/17/22 16:02, Serge Guelton wrote:
>>> I took a quick look at C++20 coroutines since they are available in
>>> compilers but the primitives look hard to use even from C++, let alone
>> >from C.
>>
>> They're C++ only in GCC, too.  I really think that QEMU should be
>> compilable in C++, but I'm not sure how easy a sell it is.
> It's perfectly fine to have one compilation unit written in C++ with a few
> symbol in `extern "C"`. No need to touch the other part of the project.

It's not just one compilation unit, it's everything that uses coroutines 
so basically all of block/.  But yes, good point---it means for example 
that you don't have to deal as much with lack of operators in C++ enums, 
which would be a huge PITA in compiling QEMU with C++.  There would 
still be some churn such as adding extern "C" blocks to headers, etc.

The main change with C++20 coroutines would be to introduce co_await, 
co_return and std::future<> everywhere, which is also a pretty 
substantial change (possibly an improvement in the case of co_await and 
co_return, but still a lot of work).

That said, it's certainly valuable to try and get at least 
tests/unit/test-coroutine.c to run with C++ coroutines, and see how much 
work that is.

Paolo