The first step would be to determine whether the value is different before you pass it through the XS interface back to Perl. Pick the smallest test that demonstrates the problem and add code to dump the value(s) to STDERR (or a file) within the C subroutine just prior to returning them.

I'd suggest dumping the 8-byte doubles in raw hex (or even binary), rather than formatted ascii, as different implementations of (s)printf can introduce changes that cloud the issues.

If you can isolate where the issues arise, it may give you a clue as to what causes it.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In reply to Re: XS optimization bug? by BrowserUk
in thread XS optimization bug? by Anonymous Monk

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