Re: [PATCH 01/18] migration/vmstate: Document vmstate_dummy

[Daniel P . Berrangé]

On Fri, Jul 03, 2020 at 10:18:54PM +0200, Philippe Mathieu-Daudé wrote:
> vmstate_dummy is special and restricted to linux-user. See commit
> c71c3e99b8 ("Add a vmstate_dummy struct for CONFIG_USER_ONLY").
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  include/migration/vmstate.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index f68ed7db13..af7d80cd4e 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -194,7 +194,7 @@ struct VMStateDescription {
>      const VMStateDescription **subsections;
>  };
>  
> -extern const VMStateDescription vmstate_dummy;
> +extern const VMStateDescription vmstate_dummy; /* Exclusively for linux-user 
> */

Originally in the commit mentioned above, this was enforced at build time:

  +#ifdef CONFIG_USER_ONLY
  +extern const VMStateDescription vmstate_dummy;
  +#endif


but this was removed in

  commit 6afc14e92ac81b29c25f097468f7751d5df1b5bc
  Author: Stefan Weil <sw@weilnetz.de>
  Date:   Fri Feb 6 22:43:10 2015 +0100

    migration: Fix warning caused by missing declaration of vmstate_dummy
    
    Warning from the Sparse static analysis tool:
    
    stubs/vmstate.c:4:26: warning:
     symbol 'vmstate_dummy' was not declared. Should it be static?


So if this is really intended to only be used by linux-user, then I
suggest we put CONFIG_USER_ONLY back, and figure out a different
way to address the undeclared symbol problem. I guess the problem
was that stub code is shared both both user/softmmu builds. So
perhaps we need to stub this in linux-user only code, instead of
having it in the main stub library that is common.


Regards,
Daniel
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