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Diffstat (limited to 'INSTALL')
| -rw-r--r-- | INSTALL | 46 |
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@@ -670,6 +670,52 @@ or by Eventually (by perl v5.6.0) this internal confusion ought to disappear, and these options may disappear as well. +=head2 64 bit support. + +If your platform does not have 64 bits natively, but can simulate them with +compiler flags and/or C<long long> or C<int64_t>, you can build a perl that +uses 64 bits. + +There are actually two modes of 64-bitness: the first one is achieved +using Configure -Duse64bitint and the second one using Configure +-Duse64bitall. The difference is that the first one is minimal and +the second one maximal. The first works in more places than the second. + +The C<use64bitint> does only as much as is required to get 64-bit +integers into Perl (this may mean, for example, using "long longs") +while your memory may still be limited to 2 gigabytes (because your +pointers could still be 32-bit). Note that the name C<64bitint> does +not imply that your C compiler will be using 64-bit C<int>s (it might, +but it doesn't have to): the C<use64bitint> means that you will be +able to have 64 bits wide scalar values. + +The C<use64bitall> goes all the way by attempting to switch also +integers (if it can), longs (and pointers) to being 64-bit. This may +create an even more binary incompatible Perl than -Duse64bitint: the +resulting executable may not run at all in a 32-bit box, or you may +have to reboot/reconfigure/rebuild your operating system to be 64-bit +aware. + +Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint +nor -Duse64bitall. + + NOTE: 64-bit support is still experimental on most platforms. + Existing support only covers the LP64 data model. In particular, the + LLP64 data model is not yet supported. 64-bit libraries and system + APIs on many platforms have not stabilized--your mileage may vary. + +=head2 Long doubles + +In some systems you may be able to use long doubles to enhance the +range and precision of your double precision floating point numbers +(that is, Perl's numbers). Use Configure -Duselongdouble to enable +this support (if it is available). + +=head2 "more bits" + +You can "Configure -Dusemorebits" to turn on both the 64-bit support +and the long double support. + =head2 Selecting File IO mechanisms Previous versions of perl used the standard IO mechanisms as defined in |