Re: Questions regarding debuginfod.h API

["Frank Ch. Eigler" <fche@redhat.com>]

Hi -

> 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!

Our pleasure!

> 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. 

(See also the DEBUGINFOD_MAXTIME and DEBUGINFOD_MAXSIZE env vars
that can limit this.)

> I would like to give the user feedback about this situation and
> ideally provide a means to cancel the download.

OK.

> 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`?

You do need to create a new client object.  You can reuse it.

> 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?

See [man debuginfod_set_progressfn].  The return code from that
progressfn callback is the ticket.


> 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?  [...]

To decide whether or not to compile in support, you'd need a
compile-time check such as for the debuginfod.h header.  (Alternately,
you could opt not to compile in support at all, and instead call out
to the debuginfod-find(1) program.)  To decide at run time whether or
not to use it, you could just use the *_find APIs and get back an
error code if things are not set up.  Or you can check the
DEBUGINFOD_URLS for being set/unset before you call in.


- FChE