cpp-example-calibration fails; displays images but does not export camera.yml

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I'm running cpp-example-calibration under Linux with a set of 6 chessboard images in an attempt to get camera distortion information. My command looks like this:

../cpp-example-calibration -w 7 -h 5 -pt chessboard -o camera.yml -op -oe imagelist.xml

and my imagelist.xml looks like this:

<?xml version="1.0"?>
<opencv_storage>
<images>
pic1.jpg pic2.jpg pic3.jpg pic4.jpg pic5.jpg pic6.jpg </images>
</opencv_storage>

a sample image from my calibration set is:

I've run this on two different Linux machines so far with the same result: Image View pops up, displays the 6 images unmodified in sequence, and then closes. This process takes 5 or so minutes, so it is doing some work, but it doesn't produce a .yml file! Does anyone have any ideas about what I'm doing wrong?