On 2/2/26 9:45 AM, Pierrick Bouvier wrote:
On 2/2/26 9:34 AM, Daniel P. Berrangé wrote:
On Mon, Feb 02, 2026 at 09:30:31AM -0800, Pierrick Bouvier wrote:
On 2/2/26 8:55 AM, Mark Cave-Ayland wrote:
On 02/02/2026 15:42, Cornelia Huck wrote:
On Mon, Feb 02 2026, Peter Maydell <[email protected]> wrote:
On Mon, 2 Feb 2026 at 04:04, Richard Henderson
<[email protected]> wrote:
On 1/30/26 04:41, Pierrick Bouvier wrote:
On 1/29/26 9:37 AM, Pierrick Bouvier wrote:
contrib/plugins: add empty cpp plugin
Hi; this fails to build for me on Linux (Ubuntu 24.04) with clang:
In file included from ../../contrib/plugins/cpp.cpp:33:
/usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/coroutine:38:3:
error: "the <coroutine> header requires -fcoroutines"
38 | # error "the <coroutine> header requires -fcoroutines"
| ^
1 error generated.
Fails for me as well on Fedora 42 (x86_64) with gcc:
In file included from ../qemu/contrib/plugins/cpp.cpp:33:
/usr/include/c++/15/coroutine:43:3: error: #error "the <coroutine> header requires
-fcoroutines"
43 | # error "the <coroutine> header requires -fcoroutines"
| ^~~~~
(It works for me on an aarch64 RHEL 9 system.)
Is this with a clean build? I had exactly the same error message
earlier, but I was able to fix it by destroying my build/ directory,
then re-running configure followed again by make.
Thanks for the reports everyone.
I tried it on ubuntu LTS and didn't encounter this problem.
What is happening is that meson unfortunately caches default_options set,
including the C++ standard version in our case.
Thus, you indeed need to clean and rebuild once.
The solution for this would be to not use default_options and add the flag
to qemu_cflags instead. It's the same limitation if we change the default
warning level, or any other option set with default_options.
If that's correct as the root cause, then it feels like this is a meson bug
that ought to be reported upstream. Any meson.build default_options changes
that affect the compiler behaviour should invalidate cache in the same way
as when we modify qemu_cflags.
I totally agree with you Daniel, and I've been bitten by that in my
previous company when updating cpp standard we used. As you can see, it
slipped out of my mind for current series...
I never understood why it had this counter intuitive behaviour, and
didn't bother to report to be honest, I simply switched to manual flags
instead at the time.
Meson devs usually have a strong opinion of how things should be, so I
don't expect this to be something that fell through the cracks but a
deliberate design choice.
EDIT: after typing the answer above, did a quick search, and indeed,
it's how it's supposed to be. So be it.
https://github.com/mesonbuild/meson/issues/13556
With regards,
Daniel
Regards,
Pierrick
Paolo, since it seems complicated to change this in meson, should we at
least remove C and C++ standard from default_options, and rely on manual
flags instead?
Probably, same goes for rust standard when we'll have to update it to 2024.
I'll let you (or anyone else on the thread more legitimate than me)
judge what's the best approach on this, and I can help to implement it
if needed.
Regards,
Pierrick
