Bug 11950 - ApplicationInfo.SharedLibraryFiles contains invalid enumerable
Summary: ApplicationInfo.SharedLibraryFiles contains invalid enumerable
Status: RESOLVED FIXED
Alias: None
Product: Android
Classification: Xamarin
Component: Bindings ()
Version: 4.6.x
Hardware: PC Windows
: Normal normal
Target Milestone: ---
Assignee: Atsushi Eno
URL:
Depends on:
Blocks:
 
Reported: 2013-04-24 17:22 UTC by info
Modified: 2013-05-23 10:18 UTC (History)
3 users (show)

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

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Status:
RESOLVED FIXED

Description info 2013-04-24 17:22:05 UTC
ApplicationInfo.SharedLibraryFiles contains a non-null value that appears to implement IList<string>, but will throw an exception whenever it is enumerated.

The following code snippet throws a NullReferenceException at the last line:

var enumerator = ApplicationInfo.SharedLibraryFiles.GetEnumerator();
if (enumerator == null) return;
enumerator.MoveNext ();

The 'enumerator' variable appears to reference a 'Android.Runtime.JavaArray`1' type, and not an actual enumerator, although a check against IEnumerator will yield true. Very strange.

Xamarin.Studio also suffers from this issue internally - when inspecting an ApplicationInfo object, the inspector will show an 'Object not initialized' message for SharedLibraryFiles instead of the error.
Comment 1 Peter Collins 2013-05-14 18:44:19 UTC
I am able to reproduce this NRE with the above code snippet on our current stable build of X.A. (4.6.4 - 03814ac5) on both Windows and OSX.
Comment 2 Jonathan Pryor 2013-05-14 20:18:43 UTC
This is a binding bug: we're not properly null-checking the return value of JNIEnv.GetObjectField(), so in this case we're effectively doing:

    public IList<string> SharedLibraryFiles {
        get {
            return new JavaArray<string> (IntPtr.Zero, JniHandleOwnership.TransferLocalRef);
        }
    }

Doomed™.

WORKAROUND: Manually perform the null check! (bleh!)

    var libs  = ApplicationInfo.SharedLibraryFiles;
    var array = libs as JavaArray<string>;
    if (array != null && array.Handle == IntPtr.Zero)
        return;
    ...
Comment 3 Jonathan Pryor 2013-05-23 09:07:57 UTC
Fixed in master/59209e6e.
Comment 4 info 2013-05-23 10:18:12 UTC
Thanks!