Re: [PATCH v5 02/24] include: define constant for early constructor priority

On 1/8/26 18:03, Daniel P. Berrangé wrote:
> Functions marked with __attribute__((__constructor__)) will be
> invoked in linker order. In theory this is well defined, but
> in practice, it is hard to determine what this order will be
> with the layers of indirection through meson, ninja and the
> static libraries QEMU builds.
> 
> Notably, the order currently appears different between Linux
> and Windows (as tested with Wine on Linux). This can cause
> problems when certain QEMU constructors have a dependancy on
> other QEMU constructors.

What dependency are you seeing, or introducing?

In theory QEMU constructors should not have any dependency, as we only 
use them to initialize static data structures (such as the various 
*_init macros).

Not an objection, but I'd like to understand this better.

Paolo

> To address this define a QEMU_CONSTRUCTOR_EARLY constant which
> provides a priority value that will run before other default
> constructors. This is to be used for QEMU constructors that
> are themselves self-contained, but may be relied upon by other
> constructors.
> 
> Reviewed-by: Richard Henderson <[email protected]>
> Reviewed-by: Dr. David Alan Gilbert <[email protected]>
> Signed-off-by: Daniel P. Berrangé <[email protected]>
> ---
>   include/qemu/compiler.h | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
> index 1c2b673c05..4c49f52eb0 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -194,6 +194,14 @@
>   # define QEMU_USED
>   #endif
>   
> +/*
> + * A priority for __attribute__((constructor(...))) that
> + * will run earlier than the default constructors. Must
> + * only be used for functions that have no dependency
> + * on global initialization of other QEMU subsystems.
> + */
> +#define QEMU_CONSTRUCTOR_EARLY 101
> +
>   /*
>    * Disable -ftrivial-auto-var-init on a local variable.
>    *