[3dprinter-general] Bug#972422: cura-engine: Segfault if using CuraEngine 4.7.1 with libarcus3 4.5

[Raphael Wimmer]

Package: cura-engine
Version: 1:4.7.1-1
Severity: normal

Dear Maintainer,

Thank you for maintaining Cura!

# Symptom:

After an upgrade from 4.5, CuraEngine 4.7.1 quits with a segfault when
called with the 'connect' parameter.
When called from Cura, the log shows this error message.

> 2020-10-18 11:00:03,264 - DEBUG - [MainThread] CuraEngineBackend.CuraEngineBackend._onBackendQuit [898]: Backend quit with return code -11. Resetting process and socke

# Probable reason:

A gdb backtrace indicates that libarcus3 is causing the segfault

> Thread 1 "CuraEngine" received signal SIGSEGV, Segmentation fault.
> 0x000055555586d318 in ?? ()
> (gdb) bt
> #0  0x000055555586d318 in ?? ()
> #1  0x00007ffff7f6bd7d in Arcus::MessageTypeStore::registerMessageType(google::protobuf::Message const*) ()
>    from /lib/x86_64-linux-gnu/libArcus.so.3
> #2  0x00007ffff7f670bc in Arcus::Socket::registerMessageType(google::protobuf::Message const*) ()
>    from /lib/x86_64-linux-gnu/libArcus.so.3

cura-engine 4.7.1 depends on libarcus3 but does not require a specific
version of this package.
Upgrading libarcus3 / python3-arcus to the current version 4.7.1 fixes
the segfault.

# Proposed solution:

Package cura-engine should require libarcus3 with same version number
(i.e. 4.7.1 at the moment).

Cheers,
Raphael