1. Carp provides for 'misreporting' the location of errors via $Carp::CarpLevel = 1;
  2. Seems right to me too. Take that with exactly as much authority as it deserves :)
  3. Seems to me there two possible ways:

    • It could yell about the possible loss of precision as a C compiler would when you assign a long double to a double.

      In that respect, when the XS code is compiled, the C compiler probably is yelling about it.

      I've looked for a proper way of pursuading XS to display warnings produced by the C compiler without success. I generally resort to adding an obviously fatal error at the end of the inline C--a # in column one of the last line works:). When the fatal error is reported, you also get to see all the warning errors that were previously kept hidden from you.

    • It could attempt to detect whether the number of significant bits set in the mantissa of the long double exceeds 53.

      *I'm not sure whether you want it to be your perl code, the XS-precompiler or the Inline generated wrappper stubs, or the C-code?

      For any given processor, or rather for a given real format, that would be a fairly simple operation. Just requiring a bit mask of the appropriate bits of the long double to check.

      For IEEE representation, you should be able to work out the appropriate bytes/bits to mask from IEEE 754 80-bit Extended double (long double) to 64-bit double unpack.

      Doing it such that it would be portable across platforms that don't use IEEE format reals could be a lot harder.

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, C doubles and -Duselongdouble by BrowserUk
in thread XS, C doubles and -Duselongdouble by syphilis

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.