Re: [Qemu-devel] [PATCH 2/2] trace: avoid SystemTap dtrace(1) warnings on empty files

[Liam Merwick]

On 21/03/2019 17:08, Stefan Hajnoczi wrote:
> target/hppa/trace-events only contains disabled events, resulting in a
> trace-dtrace.dtrace file that says "provider qemu {}".  SystemTap's
> dtrace(1) tool prints a warning when processing this input file.
>
> This patch avoids the error by emitting an empty file instead of
> "provider qemu {}" when there are no enabled trace events.
>
> Fixes: 23c3d569f44284066714ff7c46bc4f19e630583f ("target/hppa: add TLB trace 
> events")
> Reported-by: Markus Armbruster <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>


Reviewed-by: Liam Merwick <address@hidden>


> ---
>   scripts/tracetool/format/d.py | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/scripts/tracetool/format/d.py b/scripts/tracetool/format/d.py
> index 78397c24d2..c7cb2a93a6 100644
> --- a/scripts/tracetool/format/d.py
> +++ b/scripts/tracetool/format/d.py
> @@ -33,6 +33,11 @@ def generate(events, backend, group):
>       events = [e for e in events
>                 if "disable" not in e.properties]
>   
> +    # SystemTap's dtrace(1) warns about empty "provider qemu {}" but is happy
> +    # with an empty file.  Avoid the warning.
> +    if not events:
> +        return
> +
>       out('/* This file is autogenerated by tracetool, do not edit. */'
>           '',
>           'provider qemu {')