[fpc-pascal] How is EntryInformation.OS.haltproc assigned?

[Juha Manninen]

I am testing with a 64-bit Manjaro Linux.
I get an access violation when closing any LCL application built with
QT bindings using FPC trunk. When using FPC 3.0.2 there was no access
violation, and neither with other widgetsets. Only FPC trunk + QT
posed a problem.
I remember seeing this for some time, surely half a year, when testing
FPC trunk.
An app only says:
  An unhandled exception occurred at $00007F180E69437C:
  EAccessViolation:
    $00007F180E69437C
Breakpoints inside the app did not reveal anything.

I wanted to find out what is happening and built FPC trunk with debug info.
The error happens in procedure System_exit in rtl/linux/system.pp, at line:
  EntryInformation.OS.haltproc(ExitCode);

Backtrace is not very useful:
 #0 SYSTEM_EXIT at system.pp:174
 #1 fpc_do_exit at ../inc/system.inc:1076
 #2 main at project1.lpr:20

In debugger the data in both records "EntryInformation" and
"EntryInformation.OS" look valid.
Apparently the haltproc is not assigned. Where should it be assigned?
The only place under rtl/linux I find haltproc assigned is in
"si_dll.inc". There procedure _FPC_shared_lib_haltproc deals with
shared libraries. Not relevant here.

After the crash I get an assembly window pointing to this line:
 00007FFFF60AE37C 660f6f442410   movdqa 0x10(%rsp),%xmm0
Isn't xmm0 a SSE2 register or something? I don't think the compiler
generated such code.

Amazingly enough the Lazarus IDE itself when built with QT bindings
does not crash at the end. Somehow the QT bindings are quilty but how?
Any clues where I should look for the problem?

Juha