Bug#482139: [PATCH] Document that XS_VERSION_BOOTCHECK may break if $VERSION is a long enough NV

[Rafael Garcia-Suarez]

Thanks, applied to bleadperl as b017ed238008af06e2764e644dee23e72b0847ec.

2009/4/29 Niko Tyni <ntyni at debian.org>:
> As seen in <http://bugs.debian.org/482139>, using a long floating point
> number as $VERSION can make XS_VERSION_BOOTCHECK fail because of a loss
> of precision in the stringification:
>
> RRDs object version 1.2999070803 does not match bootstrap parameter 1.29990708 at /usr/lib/perl/5.10/DynaLoader.pm line 219.
>
> The mismatch happens in Perl_upg_version(), which converts a double value
> (NV) to a string with nine decimals but leaves a string value intact.
>
> Using a string as $VERSION works fine:
>
> -$VERSION=1.299907080300;
> +$VERSION="1.299907080300";
>
> so recommend this in the VERSIONCHECK entry of perlxs.pod.
> ---
>  pod/perlxs.pod |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/pod/perlxs.pod b/pod/perlxs.pod
> index c367f4c..a6e21a3 100644
> --- a/pod/perlxs.pod
> +++ b/pod/perlxs.pod
> @@ -1211,6 +1211,12 @@ To disable version checking:
>
>     VERSIONCHECK: DISABLE
>
> +Note that if the version of the PM module is an NV (a floating point
> +number), it will be stringified with a possible loss of precision
> +(currently chopping to nine decimal places) so that it may not match
> +the version of the XS module anymore. Quoting the $VERSION declaration
> +to make it a string is recommended if long version numbers are used.
> +
>  =head2 The PROTOTYPES: Keyword
>
>  The PROTOTYPES: keyword corresponds to B<xsubpp>'s C<-prototypes> and
> --
> 1.5.6.5
>
>



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