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Re^5: "goto" memory leak

by ikegami (Pope)
on Mar 31, 2016 at 02:40 UTC ( #1159173=note: print w/replies, xml ) Need Help??

in reply to Re^4: "goto" memory leak
in thread "goto" memory leak

I'm more than happy with renaming the problem to "goto creates spurious scopes".

goto doesn't create any scopes. As I've already stated, the memory is being used when my is executed since that causes it push an instruction on the stack.

Ok, but again we could argue over the definition of the word "needed". "Needed" by the program writer or "needed" by an implementation that keeps scopes around that are not accessible to the program writer anymore?

The instruction is needed because it's virtually impossible to tell that the scope will never exit.

  • A lot of things can throw exceptions.
  • Including signal handlers.
  • The program can change while it's running.

Even in the simplest cases, it would be extremely expensive to check, especially since this check would have to be performed at run-time.

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Re^6: "goto" memory leak
by jethro (Monsignor) on Mar 31, 2016 at 13:15 UTC

    Very true, it is impossible to check for scope exit. But would it be possible to check somehow (with a flag attached to the variable for example) whether the my variable already has a "destroy" POST routine on the stack or not?

      That would require extra memory for each PAD entry, and would require extra time to exit a scope, just to avoid some rare degenerate case where someone uses bad coding practices. That would be a bad tradeoff.

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