ConEmu Inside HWND Crashes Within Startup If the Parent Process Revokes HWND

[hypersw]

• Make a HWND.
• Run ConEmu with the inside-HWND parameter.
• Kill the window immediately. As it requires a yield of control on that thread, it'll actually wait until you exit the current message handler, so just spawn ConEmu.exe and either kill the HWND or the process altogether. Stopping with debugger is a good example.

=>

ConEmu asserts with

Can't create DC window!
LastError=0x00000057
The parameter is incorrect.

[Maximus5]

151217?

[hypersw]

So no.

[Maximus5]

Revokes?

[hypersw]

Destroys, or whatever. So HWND is available and valid when ConEmu gets it on the commandline, but when it tries to use this HWND, it's already gone. I guess that's the cause.

I believe what ConEmu does with HWNDs makes its and host process' threads of execution make sync cross-calls sometimes, which means that ConEmu will be waiting for the host process callback to execute. This increases the risk, as it gives the host process an explicit chance to do smth to its HWND (and waits for it).

[hypersw]

Simple repro: run conemu-inside in debugger, set a breakpoint on after starting the ConEmu process, break on it, then kill the debuggee.

[Maximus5]

https://conemu.github.io/blog/2016/02/02/Build-160202.html

[hypersw]

On a fresh build. Though looks like a new message (on some next init stage).

Repro is the same: in ConEmuSession::.ctor, after processNew.Start(), kill the WinForms-hosting process. ConEmu process is left alone in some half-inited state.

[Maximus5]

Is it fixed?

[hypersw]

Not fully. I would still see this window from time to time, rarely now though.

[hypersw]

fresh one