GNU Info

(g77-295.info)Increasing Precision/Range

---

Next: Enabling Debug Lines Prev: Support for Threads Up: Missing Features

---

Enter node , (file) or (file)node

Increasing Precision/Range
--------------------------

   Some compilers, such as `f2c', have an option (`-r8', `-qrealsize=8'
or similar) that provides automatic treatment of `REAL' entities such
that they have twice the storage size, and a corresponding increase in
the range and precision, of what would normally be the `REAL(KIND=1)'
(default `REAL') type.  (This affects `COMPLEX' the same way.)

   They also typically offer another option (`-i8') to increase
`INTEGER' entities so they are twice as large (with roughly twice as
much range).

   (There are potential pitfalls in using these options.)

   `g77' does not yet offer any option that performs these kinds of
transformations.  Part of the problem is the lack of detailed
specifications regarding exactly how these options affect the
interpretation of constants, intrinsics, and so on.

   Until `g77' addresses this need, programmers could improve the
portability of their code by modifying it to not require compile-time
options to produce correct results.  Some free tools are available
which may help, specifically in Toolpack (which one would expect to be
sound) and the `fortran' section of the Netlib repository.

   Use of preprocessors can provide a fairly portable means to work
around the lack of widely portable methods in the Fortran language
itself (though increasing acceptance of Fortran 90 would alleviate this
problem).