Hello everyone,
we are writing a program that synchronizes the OneDrive cloud service with the local computer, and run it as daemon in the background. To ensure proper database shutdown on exit, we need to install signal handlers that react to SIGINT etc.

The problem now is that at the same time we use std.net.curl.Curl, and that has some kind of bug in the shutdown routine when it is called during program termination. One always needs to manually call .shutdown, otherwise the program dumps core:
```
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00007faf58f7e967 in std.net.curl.HTTP.Impl.~this() ()
   from /usr/lib/x86_64-linux-gnu/libphobos2-ldc-shared.so.82
#2  0x00007faf58ebbce9 in _D6object__T7destroyTS3std3net4curl4HTTP4ImplZQBiFKQBeZv ()
   from /usr/lib/x86_64-linux-gnu/libphobos2-ldc-shared.so.82
#3  0x00007faf58fce020 in _D3std8typecons__T10RefCountedTSQBe3net4curl4HTTP4ImplVEQCcQCb24RefCountedAutoInitializei1ZQCv6__dtorMFZv () from /usr/lib/x86_64-linux-gnu/libphobos2-ldc-shared.so.82
#4  0x00007faf58c8d2ae in rt_finalize2 () from /usr/lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
#5  0x00007faf58c75af5 in _D2gc4impl12conservativeQw15SmallObjectPool13runFinalizersMFNbxAvZv ()
   from /usr/lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
#6  0x00007faf58c746cb in _D2gc4impl12conservativeQw3Gcx13runFinalizersMFNbxAvZv ()
   from /usr/lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
#7  0x00007faf58c7476f in _D2gc4impl12conservativeQw14ConservativeGC__T9runLockedS_DQCeQCeQCcQCnQBs13runFinalizersMFNbxAvZ2goFNbPSQDyQDyQDwQEh3GcxxQBcZvS_DQExQExQEvQFg9otherTimelS_DQFxQFxQFvQGg9numOtherslTQCzTxQDnZQFnMFNbKQDqKxQEeZv ()
   from /usr/lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
#8  0x00007faf58c75633 in _DThn16_2gc4impl12conservativeQw14ConservativeGC13runFinalizersMFNbxAvZv ()
   from /usr/lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
#9  0x00007faf58c949bc in _d_dso_registry () from /usr/lib/x86_64-linux-gnu/libdruntime-ldc-shared.so.82
#10 0x0000561068f9b3b6 in ldc.register_dso ()
#11 0x00007faf59684736 in _dl_fini () at dl-fini.c:138
#12 0x00007faf5887de3c in __run_exit_handlers (status=0, listp=0x7faf589ff718 <__exit_funcs>,
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at exit.c:108
#13 0x00007faf5887df6a in __GI_exit (status=<optimized out>) at exit.c:139
#14 <signal handler called>
```
Now, unfortunately the call to the shutdown procedure is not possible in `@nogc`, so I am a bit at loss how to deal with all this.

The code I am using is:
```
extern(C) @nogc @system void exitHandler(int value) {
       printf("Ooohhhh got %d\n", value);
       // workaround for segfault in std.net.curl.Curl.shutdown() on exit
       oneDrive.http.shutdown();
       exit(0);
}
```
and in `main` before entering the loop:
```
signal(SIGINT, &exitHandler);
```

Any suggestion would be very much appreciated.

Norbert

On Wednesday, 26 December 2018 at 03:19:45 UTC, Norbert Preining wrote:
> Hello everyone,
> we are writing a program that synchronizes the OneDrive cloud service with the local computer, and run it as daemon in the background. To ensure proper database shutdown on exit, we need to install signal handlers that react to SIGINT etc.
>
> [...]
> 
> Now, unfortunately the call to the shutdown procedure is not possible in `@nogc`, so I am a bit at loss how to deal with all this.
>
> The code I am using is:
> ```
> extern(C) @nogc @system void exitHandler(int value) {
>        printf("Ooohhhh got %d\n", value);
>        // workaround for segfault in std.net.curl.Curl.shutdown() on exit
>        oneDrive.http.shutdown();
>        exit(0);
> }
> ```
> and in `main` before entering the loop:
> ```
> signal(SIGINT, &exitHandler);
> ```
>
> Any suggestion would be very much appreciated.
>
> Norbert

The technique to use here is to wrap the non-gc code in a delegate, cast it as a @nogc delegate and call it, see [1] for more details.

[1] https://p0nce.github.io/d-idioms/#Bypassing-@nogc