Nice theory
Simply the truth.

In your run-time example, a different mechanism causes the allocations to be retained. Every sub-expression that returns a result has a "pad temp" allocated to it to store the temporary result. The values in the pad temp are retained until the sub is freed, but they are re-used. i.e. in the following: 

sub f { return "x" x $_[0] }
f(100_000); f(5); f(200_000);

[download]
a single temp will be stored within f's pad. On the first call it will hold a scalar of length 100_000, which gets retained. On the second call, the scalar is shrunk to length 5 (but not freed), and on the third call the scalar is realloced to grow to 200_000, and finally freed when the sub f is destroyed.

Dave.

In reply to Re^3: Freeing memory, revisited (Linux) by dave_the_m
in thread Freeing memory, revisited (Linux) by lkundrak

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