Re: [Valgrind-developers] [PATCH] helgrind: add --show-events debug cmdline option

[Philippe W. <phi...@sk...>]

Instead of adding separate options for each different thing you might want to trace,
it is also possible to add a single option but that accepts a set of things.

This set technique has been used e.g. for 
    --show-leak-kinds=kind1,kind2,.. which leak kinds to show?
                                            [definite,possible]
    --errors-for-leak-kinds=kind1,kind2,..  which leak kinds are errors?
                                            [definite,possible]

and accepts also =all and =none

Thanks
Philippe


On Thu, 2026-03-19 at 20:04 +0100, Paul Floyd via Valgrind-developers wrote:
> 
> On 2026-03-16 14:03, Aaron Merey via Valgrind-developers wrote:
> > SHOW_EVENTS in hg_main.c controls whether helgrind prints a trace of > its internal synchronization, threading and memory events. It is > 
> set to 0 by default to disable the trace and the only way to enable > it 
> is to modify the source code and rebuild valgrind. > > This patch 
> replaces SHOW_EVENTS with clo_show_events that is set > using the new 
> helgrind cmdline option --show-events. Information > about this option 
> is included under helgrind's --help-debug.
> Hi Aaron
> 
> I assume that there is no noticeable slowdown?
> 
> This will be good if ever we want to get any of these traces from a 
> user. Saying "run with --show-events=2" is asking a lot less than 
> "download valgrind, change a file, build it and then run the test".
> 
> Personally I think that it is best to have as many separate trace 
> options as is reasonably possible, to keep down noise from long runs.
> 
> I quite like what DRD does with
> 
>     --trace-barrier=yes|no    Trace all barrier activity [no].
>     --trace-cond=yes|no       Trace all condition variable activity [no].
>     --trace-fork-join=yes|no  Trace all thread fork/join activity [no].
>     --trace-hb=yes|no         Trace ANNOTATE_HAPPENS_BEFORE() etc. [no].
>     --trace-mutex=yes|no      Trace all mutex activity [no].
>     --trace-rwlock=yes|no     Trace all reader-writer lock activity[no].
>     --trace-semaphore=yes|no  Trace all semaphore activity [no].
> 
> If you just have one global knob like -v then there is no way to turn 
> things off (other than heavy use of awk/grep/sed etc). With multiple 
> switches you can always add more. I'm not suggesting that you break up 
> the Helgrind output like this - the DRD options reflect the DRD flow.
> 
> In the future we might want to do the same with
> 
> #define TRACE_PTH_FNS 0
> #define TRACE_QT4_FNS 0
> #define TRACE_GNAT_FNS 0
> 
> A+
> 
> Paul
> 
> 
> 
> 
> 
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