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Re: [Qemu-devel] [PATCH for 2.10] trace: ensure unique function / variab


From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCH for 2.10] trace: ensure unique function / variable names per .stp file
Date: Mon, 31 Jul 2017 10:50:23 +0100
User-agent: Mutt/1.8.3 (2017-05-23)

On Fri, Jul 28, 2017 at 02:36:57PM +0100, Daniel P. Berrange wrote:
> The simpletrace compatibility code for systemtap creates a
> function and some global variables for mapping to event ID
> numbers. We generate multiple -simpletrace.stp files though,
> one per target and systemtap considers functions & variables
> to be globally scoped, not per file. So if trying to use the
> simpletrace compat probes, systemtap will complain:
> 
>  # stap -e 'probe qemu.system.arm.simpletrace.visit_type_str { print( 
> "hello")}'
>  semantic error: conflicting global variables: identifier 
> 'event_name_to_id_map' at 
> /usr/share/systemtap/tapset/qemu-aarch64-simpletrace.stp:3:8
>         source: global event_name_to_id_map
>                        ^
>  identifier 'event_name_to_id_map' at 
> /usr/share/systemtap/tapset/qemu-system-arm-simpletrace.stp:3:8
>         source: global event_name_to_id_map
>                        ^
> 
>  WARNING: cross-file global variable reference to identifier 
> 'event_name_to_id_map' at 
> /usr/share/systemtap/tapset/qemu-system-arm-simpletrace.stp:3:8 from: 
> identifier 'event_name_to_id_map' at 
> /usr/share/systemtap/tapset/qemu-aarch64-simpletrace.stp:8:21
>  source:     if (!([name] in event_name_to_id_map)) {
>                              ^
>  WARNING: cross-file global variable reference to identifier 'event_next_id' 
> at /usr/share/systemtap/tapset/qemu-system-arm-simpletrace.stp:4:8 from: 
> identifier 'event_next_id' at :9:38
>  source:         event_name_to_id_map[name] = event_next_id
>                                               ^
> 
> We already have a string used to prefix probe names, so just
> replace '.' with '_' to get a function / variable name prefix
> 
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
>  scripts/tracetool/format/simpletrace_stap.py | 29 
> ++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)

Thanks, applied to my tracing tree:
https://github.com/stefanha/qemu/commits/tracing

Stefan

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