Re: igc statistics display

[Helmut Eller <eller.helmut@gmail.com>]

On Fri, Jan 10 2025, Gerd Möllmann wrote:

> Eli Zaretskii <eliz@gnu.org> writes:
>> SystemTap is not the ideal means for such a facility.  Its only
>> significant advantage is that it's supported by GDB.  But its huge
>> disadvantage is that it's a Linux-only facility.

I think drrace is also available for Windows.

>> In addition, I feel that this is too low-level for our purposes.  We
>> need something more akin to trace-redisplay.
>
> I must say upfront that I've only read about dtrace for a couple hours
> and asked Gemini a few questions. From that, my understanding is that an
> application can generate its own application-specific events that carry
> additional data, including strings, int, floats, and so on, structs (not
> sure if I believe Gemini in that case, but who knows). (Helmut, please
> correct me if that's wrong.)

Applications can define "static trace points".  In practice, that means
the application has macro calls like DTRACE_PROBE(name, arg1, arg2..)
in the source code at interesting places.  Obviously, the same macro
could be configured to work with dtrace or systemtap or something else.

An advantage of tools like dtrace and systemtap is that they can patch
code: static trace points are nop instructions, until activated.  So
very cheap, if not used.  Ironically, that's almost impossible to do by
the application itself.

Static trace points are useful, but with dtrace/systemtap it's also
possible to set trace points by line number, as in gdb.

Helmut