On 17/07/2018 12:16, Cameron Simpson wrote:
On 17Jul2018 10:10, Robin Becker <ro...@reportlab.com> wrote:
A user reported an infinite loop in reportlab. I determined a possible cause and fix and would like to test for absence of the
loop. Is there any way to check for presence/absence of an infinite loop in python? I imagine we could do something like call an
external process and see if it takes too long, but that seems a bit flaky.
While others have kindly pointed you at the halting problem (unsolvable in the general case) you can usually verify that the
specific problem you fixed is fixed. Can you figure out how long the task should run with your fix in a test case? Not as time,
but in loop iterations? Put a counter in the loop and check that its value doesn't exceed that.
well I understand the problem about not halting. However as you point out in a fixed case I know that the test should take
fractions of a second to complete. I certainly don't want to put instrumentation into the source code. It's relatively easy to
imagine polling termination of a separate thread/process, but that's not particularly reliable. I don't know if there is a way to
ask a python interpeter how many instructions it has carried out.
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Robin Becker
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