in reply to Re^3: Windows / Linux puzzler
in thread Windows / Linux puzzler

I think Veltro's point is likely irrelevant if both the Windows perl and Linux perl report the same value for $Config{nvsize}.

In at least some verisons of Perl, creating a float from a string is done by the underlying C library, and MS's library is known to not be as good as a gcc's.

Image showing the output varies by compiler

I didn't include nvsize in the screenshot, but both builds use IEEE double-precision floats.

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Re^5: Windows / Linux puzzler
by syphilis (Archbishop) on Mar 26, 2020 at 02:25 UTC
    MS's library is known to not be as good as a gcc's


    All that the linked example demonstrates is that there's a discrepancy in the %.20g formatting - it says nothing about the ability to assign values correctly.
    If you compare the actual values by doing "%a" formatting on both the Linux and windows perls, you'll see that 0.1 is exactly the same double.
    Also, I believe the OP's activestate perl was built with (mingw port of) gcc. They stopped using Microsoft compilers a few years ago.

    ikegami's point is likely even more irrelevant than Veltro's.

    Cheers,
    Rob
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      If you compare the actual values by doing "%a" formatting on both the Linux and windows perls, you'll see that 0.1 is exactly the same double.

      Your are correct. pack 'd' shows this more definitely. 

      >perl -E"say sprintf '%vX', pack 'd>', $ARGV[0]" 0.1
3F.B9.99.99.99.99.99.9A

      [download]
      $ perl -E'say sprintf "%vX", pack "d>", $ARGV[0]', 0.1
3F.B9.99.99.99.99.99.9A

      [download]

      I believe the OP's activestate perl was built with (mingw port of) gcc

      It definitely allows mingw to be used to compile modules, but I don't know if that's what used to build Perl itself. (Update: perl -V hints that it uses mingw)

      I beleive Strawberry Perl uses mingw, and I used Strawberry Perl in the test in the earlier post. If so, there are pertinent differences in the libraries between mingw and gcc.

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        there are pertinent differences in the libraries between mingw and gcc

        I think that with mingw, the MS runtime is still used by default for formatting of values.
        However, that is avoided (by building with -D__USE_MINGW_ANSI_STDIO) in recent versions of Strawberry Perl, beginning perl-5.26.0.
        (Look for "-D__USE_MINGW_ANSI_STDIO" in perl -V:ccflags)

        Of course, ActiveState don't build with -D__USE_MINGW_ANSI_STDIO.

        Cheers,
        Rob
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