Add support for SD_EVENT_DEFAULT

Currently, sd-event supports the ability to have a thread-local default
event loop. However, this is less useful than it can be since all functions
which require an sd_event* as input require the caller to pass it. This
patch adds a new macro which allows the developer to pass a constant
SD_EVENT_DEFAULT instead. This reduces work for the caller.

For example:

    r = sd_event_default(&e);
    r = sd_event_add_io(e, ...);
    sd_event_unref(e);

Becomes:

    r = sd_event_add_io(SD_EVENT_DEFAULT, ...);

If no thread-local default event loop exists, the function calls will
return -ENOPKG. No event loop will ever be implicitly created.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/systemd/sd-event.h b/src/systemd/sd-event.h
index 9083d5fa9..57c1692fc 100644
--- a/src/systemd/sd-event.h
+++ b/src/systemd/sd-event.h
@@ -40,6 +40,8 @@
 
 _SD_BEGIN_DECLARATIONS;
 
+#define SD_EVENT_DEFAULT ((sd_event *) 1)
+
 typedef struct sd_event sd_event;
 typedef struct sd_event_source sd_event_source;