Bug 54919 - NSFormatter subclass sample does not work in static registrar
Summary: NSFormatter subclass sample does not work in static registrar
Alias: None
Product: Xamarin.Mac
Classification: Desktop
Component: Runtime ()
Version: 3.2.0 (15.1)
Hardware: PC Mac OS
: Normal normal
Target Milestone: 15.3
Assignee: Rolf Bjarne Kvinge [MSFT]
Depends on:
Reported: 2017-04-10 10:12 UTC by Maxim Kosov
Modified: 2017-07-04 12:46 UTC (History)
5 users (show)

Tags: 15.1R
Is this bug a regression?: ---
Last known good build:

app with reproduce and a crash log (371.44 KB, application/zip)
2017-04-10 10:12 UTC, Maxim Kosov

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Description Maxim Kosov 2017-04-10 10:12:07 UTC
Created attachment 21382 [details]
app with reproduce and a crash log

NSTextField with custom NSFormatter crashes application when compiled in Release mode after update to Xamarin.Mac
Works in Debug mode. Worked more than half a year before the update.

How to reproduce:
1. Create subclass of NSFormatter
2. Add NSTextField to the UI
3. Add NSFormatter to created text field (no matter how to add: manually with code or IB)
4. Compile and run in Release. Input any character into created text field.

Actual result:
Application crashes (crash log and sample app in attachments)
Comment 1 Chris Hamons 2017-04-10 14:44:01 UTC
In 3.2 a few defaults in Xamarin.Mac were changed:


and one of them (use of the static registrar) is the culprit here.

You can swap back to the old behavior by adding 


to your Project Options -> Build -> Mac Build -> Additional mmp arguments section.

I'll have to look into what the static registrar isn't playing nicely with NSFormatter subclasses.
Comment 2 Rolf Bjarne Kvinge [MSFT] 2017-05-18 12:08:36 UTC
GetObjectValue is defined as this:

    [Export ("getObjectValue:forString:errorDescription:")]
    bool GetObjectValue (out NSObject obj, string str, out NSString error);

and is called with "pointer, pointer, NULL":

frame #1: 0x00000001096e85a6 NSFormatterCrash`::-[CustomFormatter getObjectValue:forString:errorDescription:](self=0x0000610000037680, _cmd="getObjectValue:forString:errorDescription:", p0=0x00007fff568597e0, p1=class name = NSBigMutableString, p2=0x0000000000000000) at registrar.m:37453

the problem is that C# requires "out" parameters to be non-null, so the static registrar assumes the same thing, and does generates this upon returning from the managed function to copy the out parameters back to native code:

-> 21008		*p2 = (id) handle2;

which crashes, since "p2 = NULL".
Comment 3 Rolf Bjarne Kvinge [MSFT] 2017-05-18 13:55:37 UTC
master: https://github.com/xamarin/xamarin-macios/pull/2106