Re: Portable inline asm to get address of TLS variable

[Paolo Bonzini <pbonzini@redhat.com>]

On 2/17/22 10:28, Stefan Hajnoczi wrote:
>> But going against ABI and toolchain in this way is really no long-term
>> solution.  You need to switch to stackless co-routines, or we need to
>> provide proper ABI-level support for this.  Today it's the thread
>> pointer, tomorrow it's the shadow stack pointer, and the day after that,
>> it's the SafeStack pointer.  And further down the road, it's some thread
>> state for garbage collection support.  Or something like that.
> 
> Yes, understood :(. This does feel like solving an undefined behavior
> problem by adding more undefined behavior on top!

Yes, this is the kind of thing that I generally despise when I see other 
programs do it...  it's easy to dig ourselves in the same hole.

> 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.

Paolo