Bug 16318 - List<T> initializes to different size than Microsoft compiled CIL
Summary: List<T> initializes to different size than Microsoft compiled CIL
Alias: None
Product: Class Libraries
Classification: Mono
Component: mscorlib ()
Version: 3.2.x
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Marek Safar
Depends on:
Reported: 2013-11-18 12:28 UTC by Stephen Rawlins
Modified: 2013-11-29 14:40 UTC (History)
5 users (show)

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

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Description Stephen Rawlins 2013-11-18 12:28:56 UTC
The following test passes on Microsoft Windows/Visual Studio, but fails on Mac/Xamarin/Mono implementation:

public void ItemsCollectionCapacity()
	string[] input = { "Brachiosaurus", 
          "Mamenchisaurus" };

	List<string> dinosaurs = new List<string>(input);
	Assert.AreEqual(3, dinosaurs.Capacity);

On the Xamarin/Mono execution, the initial capacity is 4 (vs. 3 on Windows).

It appears that Windows sets the initial collection's capacity to 3 (based on the 3-element input supplied with the constructor call), whereas Xamarin appears to first allocate the "()" (empty constructor) List - which sets initial capacity at 2 - and subsequently grows by doubling, so the 3rd element bumps capacity up to 4.

When executed on Xamarin/Mono, the test fails with:

  Expected: 3
  But was: 4 

This difference causes cross-platform testing to fail.
Comment 1 Marek Safar 2013-11-29 14:40:59 UTC
Fixed in master