Re: [PATCH] Avoid depending on destructor order

[Jason Merrill <jason@redhat.com>]

On 9/23/22 10:12, Thomas Neumann wrote:
>>
>>     +static const bool in_shutdown = false;
>>
>> I'll let Jason or others decide if this is the right solution.  It 
>> seems that in_shutdown also could be declared outside the #ifdef and 
>> initialized as "false".
> 
> sure, either is fine. Moving it outside the #ifdef wastes one byte in 
> the executable (while the compiler can eliminate the const), but it does 
> not really matter.

Might as well go with your patch, then, adding a comment to explain why 
the variable is defined in two places.

> I have verified that the patch below fixes builds for both fast-path and 
> non-fast-path builds. But if you prefer I will move the in_shutdown 
> definition instead.
> 
> Best
> 
> Thomas
> 
> PS: in_shutdown is an int here instead of a bool because non-fast-path 
> builds do not include stdbool. Not a good reason, of course, but I 
> wanted to keep the patch minimal and it makes no difference in practice.
> 
> 
>      When using the atomic fast path deregistering can fail during
>      program shutdown if the lookup structures are already destroyed.
>      The assert in __deregister_frame_info_bases takes that into
>      account. In the non-fast-path case however is not aware of
>      program shutdown, which caused a compiler error on such platforms.
>      We fix that by introducing a constant for in_shutdown in
>      non-fast-path builds.
> 
>      libgcc/ChangeLog:
>              * unwind-dw2-fde.c: Introduce a constant for in_shutdown
>              for the non-fast-path case.
> 
> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
> index d237179f4ea..0bcd5061d76 100644
> --- a/libgcc/unwind-dw2-fde.c
> +++ b/libgcc/unwind-dw2-fde.c
> @@ -67,6 +67,8 @@ static void
>   init_object (struct object *ob);
> 
>   #else
> +/* Without fast path frame deregistration must always succeed.  */
> +static const int in_shutdown = 0;
> 
>   /* The unseen_objects list contains objects that have been registered
>      but not yet categorized in any way.  The seen_objects list has had
>