This macro will read a pointer of any type, return it, and set the
pointer to NULL. This is useful as an explicit concept of passing
ownership of a memory area between pointers.
This takes inspiration from Rust:
https://doc.rust-lang.org/std/option/enum.Option.html#method.take
and was suggested by Alan Jenkins (@sourcejedi).
It drops ~160 lines of code from our codebase, which makes me like it.
Also, I think it clarifies passing of ownership, and thus helps
readability a bit (at least for the initiated who know the new macro)
Object path components must start with [A-Za-z_] (AFAIK).
Also the value of 'p' is undefined if asprintf fails.
Compare to user_bus_path() in src/login/logind-user-dbus.c:281.
Only the very basics, more to come.
For now:
$ busctl tree org.freedesktop.network1
└─/org/freedesktop/network1
└─/org/freedesktop/network1/link
├─/org/freedesktop/network1/link/1
├─/org/freedesktop/network1/link/2
├─/org/freedesktop/network1/link/3
├─/org/freedesktop/network1/link/4
├─/org/freedesktop/network1/link/5
├─/org/freedesktop/network1/link/6
├─/org/freedesktop/network1/link/7
├─/org/freedesktop/network1/link/8
└─/org/freedesktop/network1/link/9
$ busctl introspect org.freedesktop.network1 /org/freedesktop/network1
NAME TYPE SIGNATURE RESULT/VALUE FLAGS
org.freedesktop.network1.Manager interface - - -
.OperationalState property s "carrier" emits-change
$ busctl introspect org.freedesktop.network1 /org/freedesktop/network1/link/1
NAME TYPE SIGNATURE RESULT/VALUE FLAGS
org.freedesktop.network1.Link interface - - -
.AdministrativeState property s "unmanaged" emits-change
.OperationalState property s "carrier" emits-change
Lennart Poettering