net_server: crash when receiving B_ABOUT_REQUESTED

[X512]

This is hrev54837.

Steps to reproduce:

1. Run in Terminal: hey application/x-vnd.haiku-net_server '_ABR'.
2. net_server will crash.

net_server implements B_ABOUT_REQUESTED handling here: ​https://git.haiku-os.org/haiku/tree/src/servers/net/NetServer.cpp#n158.

While testing I found that only debug_server correctly responts to B_ABOUT_REQUESTED message. Other servers and most applications do nothing.

[X512]

Note that it crash in BTextView initialization.

[jscipione]

I guess this must be something I've overlooked in BTextView _UpdateInsets() (NULL pointer exception or similar).

[jscipione]

be_control_look is NULL in BAlert::_Init(). How is that possible? How to fix?

[pulkomandy]

Probably because net_server is started early (before app_server) and initializing the control look needs collaboration from app_server?

I suggest just removing the about box from net_server. We don't need to have about boxes in each and every executable.

[jscipione]

Unfortunately no, net_server starting before app_server is not it because I restarted my net_server. I believe that the problem is that BAlert inherits from BWindow and so there's no connection to app_server during BWindow constructor. To fix this we have to run _Init() after the object is constructed in another method or by making the connection to app server early.

I'm pretty sure net_server doesn't really have an about box anyway, but unfortunately that doesn't stop somebody from using hey to send net_server an AboutRequested ('_ABR') message.

I don't know what BWindow method to use that will run right after the object is constructed. There's no AttachedToWindow() or AllAttached() for a BWindow, only a BView. Could I put _Init() in Run() perhaps? Could I attach a BView to BAlert and then attach everything else as a child to that view in AttachedToWindow()?

In any case, there's no bug in BTextView so I didn't cause this crash, it just happened to be the first time be_control_look was used. It's one of the few pointers used in BTextView::_UpdateInsets() so it was pretty easy to track down that a NULL be_control_look was the cause. Skipping over _UpdateInsets() just makes net_server crash a bit later when it tries to use be_control_look in a different place.

[pulkomandy]

I'm pretty sure net_server doesn't really have an about box anyway, but unfortunately that doesn't stop somebody from using hey to send net_server an AboutRequested ('_ABR') message.

The code in net_server that runs the BAlert is linked in the ticket description. We just need to empty that method and nothing will happen when the message is received.

I believe that the problem is that BAlert inherits from BWindow and so there's no connection to app_server during BWindow constructor. To fix this we have to run _Init() after the object is constructed in another method or by making the connection to app server early.

No, the fix is to make sure the window is created after the app_server connection is established (by creating a BApplication), or, if there is no BApplication, not try to open a window, because that's not allowed without a BApplication, and various strange things will happen if you try to do it anyway.

[jscipione]

OK I see now, let's remove the offending code if not needed. No BApplication, no about dialog, got it.

[pulkomandy]

Fixed in hrev55293.