I would not have considered cases 2, 3 or 6 false positives

Why not? A warning would be issued for complete, accurate, functioning code. That's the very definition of a false positive.

#2 ignores one of the function's return values. There are other ways of doing it, but there's nothing wrong with that way.

#3 implements creates an empty file.

#6 is used in creating inside out objects.

#1 uses $foo++

No. As far as Perl is concerned, '$foo++' might as well be 'print "Hello World"' when the program is compiled. $foo is only seen long after the warning has been issued, when the eval is executed.

#4 in theory will see $lock checked at least once inside do_stuff_that_needs_the_lock()

No. It's not passed to do_stuff_that_needs_the_lock (which would be using it twice).

#5 passes $tree to new()

Yeah, but what about $sentinel?

#4 and #5 are both examples of Resource Acquisition Is Initialization objects where the functionality exists solely in the constructor and the (implicitly called) destructor.

In reply to Re^3: Warnings on unused variables? by ikegami
in thread Warnings on unused variables? by AZed

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