(The following information augments or overrides the information in
Section 1.4 of ANSI X3.9-1978 FORTRAN 77 in specifying the GNU Fortran
language. Chapter 1 of that document otherwise serves as the basis for
the relevant aspects of GNU Fortran.)
The definition of the GNU Fortran language is akin to that of the
ANSI FORTRAN 77 language in that it does not generally require
conforming implementations to diagnose cases where programs do not
conform to the language.
However, `g77' as a compiler is being developed in a way that is
intended to enable it to diagnose such cases in an easy-to-understand
A program that conforms to the GNU Fortran language should, when
compiled, linked, and executed using a properly installed `g77' system,
perform as described by the GNU Fortran language definition. Reasons
for different behavior include, among others:
* Use of resources (memory--heap, stack, and so on; disk space; CPU
time; etc.) exceeds those of the system.
* Range and/or precision of calculations required by the program
exceeds that of the system.
* Excessive reliance on behaviors that are system-dependent
(non-portable Fortran code).
* Bugs in the program.
* Bug in `g77'.
* Bugs in the system.
Despite these "loopholes", the availability of a clear specification
of the language of programs submitted to `g77', as this document is
intended to provide, is considered an important aspect of providing a
robust, clean, predictable Fortran implementation.
The definition of the GNU Fortran language, while having no special
legal status, can therefore be viewed as a sort of contract, or
agreement. This agreement says, in essence, "if you write a program in
this language, and run it in an environment (such as a `g77' system)
that supports this language, the program should behave in a largely
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