Questions regarding debuginfod.h API

[Milian Wolff <mail@milianw.de>]

Hey all,

now that archlinux is supporting debuginfod, I have finally tried it out. It's 
such a game changer, many thanks for everyone involved in working on this!

Now to my question: In applications using elfutils, we will now automatically 
download debug information when DEBUGINFOD_URLS is defined. But doing that can 
take a very long time. I would like to give the user feedback about this 
situation and ideally provide a means to cancel the download.

Looking at `debuginfod.h` I `debuginfod_set_progressfn` which looks ideal. But 
how do I access the default `debuginfod_client *` which seems to exist without 
me ever calling `debuginfod_begin` anywhere? Or do I need to create a new 
client here via `debuginfod_begin`?

Then, how would I cancel an ongoing download job? GDB seems to do that when I 
press `CTRL+C`, but I do not see any API I could use for that purpose?

Finally, what is the recommended way to check whether debuginfod is available? 
Should one rely on the build system to discover the `debuginfod.h` header 
file, or is some other compile time check suggested to detect it? I'm asking, 
because while I want to add the above API to get a better debuginfod 
experience, I do not necessarily want to raise the minimum elfutils version 
requirement just for that purpose.

Many thanks again!
-- 
Milian Wolff
http://milianw.de