Aborting from core/sync/mutex.d(147) Error: pthread_mutex_init failed.

[mitchell]

On Wednesday, 1 April 2020 at 02:08:09 UTC, mitchell wrote:
> Hello,
>
> I've just finished migrating a project from GDC/Makefile to LDC 
> with dub. The program now compiles and runs, and works fine 
> until such time as the following error occurs:
>
> Aborting from core/sync/mutex.d(147) Error: pthread_mutex_init 
> failed.
>
> out of GDB, the whole text is:
>
> Aborting from core/sync/mutex.d(147) Error: pthread_mutex_init 
> failed.
> Thread 1 "squares" received signal SIGABRT, Aborted.
> [Switching to Thread 0x7ffff74a7580 (LWP 7576)]
> __GI_raise (sig=sig at entry=6) at 
> ../sysdeps/unix/sysv/linux/raise.c:50
> 50	../sysdeps/unix/sysv/linux/raise.c: No such file or 
> directory.
>
> and the backtrace is (sorry for info dump):
>
> #0  __GI_raise (sig=sig at entry=6) at 
> ../sysdeps/unix/sysv/linux/raise.c:50
> #1  0x00007ffff76eb535 in __GI_abort () at abort.c:79
> #2  0x00007ffff7ac4fa7 in 
> _D4core8internal5abortQgFNbNiNfMAyaMQemZv ()
>    from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #3  0x00007ffff7acd7e3 in core.sync.mutex.Mutex.~this() ()
>    from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #4  0x00007ffff7af12ae in rt_finalize2 () from 
> /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #5  0x00007ffff7adb7bf in 
> _D2gc4impl12conservativeQw3Gcx5sweepMFNbZm ()
>    from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #6  0x00007ffff7ad89b2 in 
> _D2gc4impl12conservativeQw3Gcx11fullcollectMFNbbZm ()
>    from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #7  0x00007ffff7ada126 in 
> _D2gc4impl12conservativeQw3Gcx10smallAllocMFNbhKmkZPv ()
>    from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #8  0x00007ffff7ad6c44 in 
> _D2gc4impl12conservativeQw14ConservativeGC__T9runLockedS_DQCeQCeQCcQCnQBs12mallocNoSyncMFNbmkKmxC8TypeInfoZPvS_DQEgQEgQEeQEp10mallocTimelS_DQFiQFiQFgQFr10numMallocslTmTkTmTxQCzZQFcMFNbKmKkKmKxQDsZQDl () from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #9  0x00007ffff7ad92df in 
> _DThn16_2gc4impl12conservativeQw14ConservativeGC6qallocMFNbmkxC8TypeInfoZS4core6memory8BlkInfo_ () from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #10 0x00007ffff7addbd0 in gc_qalloc () from 
> /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #11 0x00007ffff7ac9fb2 in 
> _D4core6memory2GC6qallocFNaNbmkxC8TypeInfoZSQBqQBo8BlkInfo_ ()
>    from /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #12 0x00007ffff7af0519 in _d_newarrayU () from 
> /lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
> #13 0x00005555556b9682 in 
> _D7squares4core5coord5Coord9adjacentsMxFNdZASQBrQBmQBkQBh 
> (this=...)
>     at 
> /home/mitchell/Apps/D/games/squares/src/squares/core/coord.d:102
>
> There are several frames above #13 here, but #13 is the last 
> line of "my" code, and the deeper ones (appear?) to be runtime 
> and phobos stuff.The lines immediately around coord.d:102 are:
>
>     Coord[] adjacents() const @property
>     {
>         return [ right, up, left, down ]; // line 102
>     }
>
> which are defined in a struct called "Coord". I suspect that 
> there isn't something wrong specifically with this line, and 
> instead something more "amazingly" wrong. Given that this 
> worked fine with the previous (and older) version of GDC which 
> I used before my migration, I don't know what could be wrong.
>
> I'm just not entirely certain where to start looking for 
> problems. If this issue is over-broad, I'm sorry. Elsewhere in 
> the program, I make use of the core.thread and Thread things, 
> however that implementation seems fairly straightforward and 
> fine, and never had issues under the old compiler.
>
> Any and all help is appreciated!

I have (surprisingly) figured out the issue myself. I guess I 
didn't think about this before, but the background thread 
(elsewhere in the application) keeps a few mutexes such that it 
can pass work to the main thread (for changing UI things, and 
such) and it appears that after the background task is completed, 
there is at least one mutex which was still held in a locked 
state. The error arises (as can been seen from the stack trace) 
when that mutex is being destructed. As my underlying system is 
unix, the pthread object beneath mutex is destroyed, but 
according to the documentation 
(https://linux.die.net/man/3/pthread_mutex_destroy) destroying a 
mutex while it's still locked can cause an error. After I fixed 
my implementation to ensure that all mutexes are unlocked on the 
appropriate threads before they can be destructed, the issue went 
away. Apparently my old compiler either handled that issue for me 
automatically, or it just wasn't being detected.

TLDR: pebkac