How to ideally fix the log function

[Andrew Jeffery]

On Thu, 25 Jul 2019, at 20:52, vishwa wrote:
> Hi John,
> 
> Just some background; The goal is not to have func() pass in CODE_LINE 
> and CODE_FUNC since it would be a huge change all over in the code.

There's no way this is really going to work. It turns out sd_journal_print()
is actually a macro that adds the CODE_* properties via __LINE__ etc when
SD_JOURNAL_SUPPRESS_LOCATION is not defined[1], so we either get
the misleading information or force the caller to provide it.

A hack approach that almost immediately falls short is that you could try
macro over log() and adjust the actual log function prototype to take in the
location parameters so we can call sd_journal_send_with_location()
directly. However macro-ing over log won't handle namespaces correctly,
and log() seems to parameterise the level with a template so we can't
define the hypothetical log macro as a macro function (which we need to
do in order to adjust the parameter list).

Having said all that I'm not really a C++ person, but it appears the API has
trapped itself in a C++ corner. Maybe people more experienced and creative
than I can come up with something, but I think the best thing we can do
is three-fold:

1. Build libsystemd with `CFLAGS=-DSD_JOURNAL_SUPPRESS_LOCATION`
2. Add a new log macro that allows us to capture the info properly
3. Change callsites to the new macro function over time.

With 1 we remove the misleading information from the journal, and 2 and 3
get us to the right place, eventually at the expense of CPP macros.

Andrew

[1] https://github.com/systemd/systemd/blob/master/src/systemd/sd-journal.h#L53