Re^2: Memory usage double expected (run-time)

> Try $x = 'a' x (2**${\32});

yes, forcing the creation of the RHS into runtime works.

edit

Dave_The_M will know better, why the space of an inline constant wasn't released.

I suppose it's just an overlooked optimization.

Cheers Rolf
_{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :)

Wikisyntax for the Monastery}

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Re^3: Memory usage double expected (run-time) by eyepopslikeamosquito (Archbishop) on Oct 27, 2022 at 12:06 UTC
Tim Bunce's excellent Profiling Memory Usage talk gives some insight into what's going on at the 09:20 minute mark: `sub foo { my $var = "X" x 10_000_000; } foo();` [download] Tim explains that: The buffer for the `$var` lexical is preserved (for next time you call the subroutine). The compiler says hey `"X"` is a constant and `10_000_000` is a constant, so I'm gonna build you a 10 MB constant! And I'm going to keep it here to one side so when you call this subroutine again I can just copy it in for you! (aka Constant folding). With recursion, things get much worse (sorry, I couldn't bring myself to watch that part :). Though Tim's Devel::SizeMe module might be useful, AFAIK it is up for adoption and not being actively developed ATM. I also keep a list of Memory Tools References (from this list, Mini-Tutorial: Perl's Memory Management by ikegami is definitely worth reading).	[reply] [d/l] [select]
Re^4: Memory usage double expected (run-time) by LanX (Saint) on Oct 27, 2022 at 12:15 UTC
OK this makes sense. Perl can't know beforehand, how often this line is executed. Even if it cared to check that it's not inside a loop or sub. Cheers Rolf _{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :) Wikisyntax for the Monastery}	[reply]
Re^3: Memory usage double expected (run-time) by dave_the_m (Monsignor) on Oct 27, 2022 at 12:17 UTC
My initial thoughts: In general an assign should COW, but the rules are complex. It's not happening in this case. It's probably a bug. Dave.	[reply]
Re^3: Memory usage double expected (run-time) by cavac (Prior) on Oct 27, 2022 at 10:40 UTC
Maybe the string is different in memory depending on when it is created? Unicode vs ASCII or something? PerlMonks XP is useless? Not anymore: XPD - Do more with your PerlMonks XP	[reply]
Re^4: Memory usage double expected (run-time) by LanX (Saint) on Oct 27, 2022 at 12:13 UTC
nope, I think eyepops explanation is spot on. Cheers Rolf _{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :) Wikisyntax for the Monastery}	[reply]