Why does Perl's Devel::LeakTrace::Fast point to blank files and evals?

Question

I am using Devel::LeakTrace::Fast to debug a memory leak in a perl script designed as a daemon which runs an infinite loop with sleeps until interrupted. I am having some trouble both reading the output and finding documentation to help me understand the output. The perldoc doesn't contain much information on the output. Most of it makes sense, such as pointing to globals in DBI. Intermingled with the output, however, are several

leaked SV(<LOCATION>) from (eval #) line #

Where the numbers are numbers and <LOCATION> is a location in memory. The script itself is not using eval at any point - I have not investigated each used module to see if evals are present. Mostly what I want to know is how to find these evals (if possible).

I also find the following entries repeated over and over again

leaked SV(<LOCATION>) from  line #

Where line # is always the same #. Not very helpful in tracking down what file that line is in.

Answer 1

You may not be using eval anywhere directly, but some module you are using likely is. Additionally, there could be a problem in some XS code you are linking into.

Have you tried reducing your script bit by bit, cutting out parts that you think might be suspect (or even parts that you think are not), and seeing how your results change? If you can split your script up into discrete pieces (which is a good idea to do anyway, from an architectural and maintainability standpoint), you might be able to find which area is the culprit, and then drill down from there.