device: don't let subclasses call NMDevice's act_stage1_prepare()

NMDevice's act_stage1_prepare() now does nothing. Calling it is not
useful and has no effect.

In general, when a subclass overwrites a virtual function, it must be
defined whether the subclass must, may or must-not call the parents
implementation. Likewise, it must be clear when the parents
implementation should be chained: first, as last, does it matter?
In any case, that very much depends on how the parent is implemented
and this can only be solved by documentation and common conventions.

It's a forgiving approach to have a parents implementation do nothing,
then the subclass may call it at any time (or not call it at all).
This is especially useful if classes don't know their parent class well.
But in NetworkManager code the relationship between classes are known
at compile time, so every of these classes knows it derives directly
from NMDevice.

This forgingin approach was what NMDevice's act_stage1_prepare() was doing.
However, it also adds lines of code resulting in a different kind of complexity.
So, it's not clear that this forgiving approach is really better. Note
that it also has a (tiny) runtime and code-size overhead.

Change the expectation of how NMDevice's act_stage1_prepare() should be
called: it is no longer implemented, and subclasses *MUST* not chain up.

1 files changed, 0 insertions, 5 deletions

diff --git a/src/devices/wwan/nm-device-modem.c b/src/devices/wwan/nm-device-modem.c
index 29c51162d0..be0993916d 100644
--- a/src/devices/wwan/nm-device-modem.c
+++ b/src/devices/wwan/nm-device-modem.c
@@ -583,13 +583,8 @@ deactivate_async (NMDevice *self,
 static NMActStageReturn
 act_stage1_prepare (NMDevice *device, NMDeviceStateReason *out_failure_reason)
 {
-	NMActStageReturn ret;
 	NMActRequest *req;
 
-	ret = NM_DEVICE_CLASS (nm_device_modem_parent_class)->act_stage1_prepare (device, out_failure_reason);
-	if (ret != NM_ACT_STAGE_RETURN_SUCCESS)
-		return ret;
-
 	req = nm_device_get_act_request (device);
 	g_return_val_if_fail (req, NM_ACT_STAGE_RETURN_FAILURE);