g77.texi

gcc-2.95.3 Linux下最常用的C编译器

Public License instead of this License.

@node Contributors
@unnumbered Contributors to GNU Fortran
@cindex contributors
@cindex credits

In addition to James Craig Burley, who wrote the front end,
many people have helped create and improve GNU Fortran.

@itemize @bullet
@item
The packaging and compiler portions of GNU Fortran are based largely
on the GNU CC compiler.
@xref{Contributors,,Contributors to GNU CC,gcc,Using and Porting GNU CC},
for more information.

@item
The run-time library used by GNU Fortran is a repackaged version
of the @code{libf2c} library (combined from the @code{libF77} and
@code{libI77} libraries) provided as part of @code{f2c}, available for
free from @code{netlib} sites on the Internet.

@item
Cygnus Support and The Free Software Foundation contributed
significant money and/or equipment to Craig's efforts.

@item
The following individuals served as alpha testers prior to @code{g77}'s
public release.  This work consisted of testing, researching, sometimes
debugging, and occasionally providing small amounts of code and fixes
for @code{g77}, plus offering plenty of helpful advice to Craig:

@itemize @w{}
@item
Jonathan Corbet
@item
Dr.@: Mark Fernyhough
@item
Takafumi Hayashi (The University of Aizu)---@email{takafumi@@u-aizu.ac.jp}
@item
Kate Hedstrom
@item
Michel Kern (INRIA and Rice University)---@email{Michel.Kern@@inria.fr}
@item
Dr.@: A. O. V. Le Blanc
@item
Dave Love
@item
Rick Lutowski
@item
Toon Moene
@item
Rick Niles
@item
Derk Reefman
@item
Wayne K. Schroll
@item
Bill Thorson
@item
Pedro A. M. Vazquez
@item
Ian Watson
@end itemize

@item
Scott Snyder (@email{snyder@@d0sgif.fnal.gov})
provided the patch to add rudimentary support
for @code{INTEGER*1}, @code{INTEGER*2}, and
@code{LOGICAL*1}.
This inspired Craig to add further support,
even though the resulting support
would still be incomplete, because version 0.6 is still
a ways off.

@item
David Ronis (@email{ronis@@onsager.chem.mcgill.ca}) inspired
and encouraged Craig to rewrite the documentation in texinfo
format by contributing a first pass at a translation of the
old @file{g77-0.5.16/f/DOC} file.

@item
Toon Moene (@email{toon@@moene.indiv.nluug.nl}) performed
some analysis of generated code as part of an overall project
to improve @code{g77} code generation to at least be as good
as @code{f2c} used in conjunction with @code{gcc}.
So far, this has resulted in the three, somewhat
experimental, options added by @code{g77} to the @code{gcc}
compiler and its back end.

(These, in turn, have made their way into the @code{egcs}
version of the compiler, and do not exist in @code{gcc}
version 2.8 or versions of @code{g77} based on that version
of @code{gcc}.)

@item
John Carr (@email{jfc@@mit.edu}) wrote the alias analysis improvements.

@item
Thanks to Mary Cortani and the staff at Craftwork Solutions
(@email{support@@craftwork.com}) for all of their support.

@item
Many other individuals have helped debug, test, and improve @code{g77}
over the past several years, and undoubtedly more people
will be doing so in the future.
If you have done so, and would like
to see your name listed in the above list, please ask!
The default is that people wish to remain anonymous.
@end itemize

@node Funding
@chapter Funding Free Software

If you want to have more free software a few years from now, it makes
sense for you to help encourage people to contribute funds for its
development.  The most effective approach known is to encourage
commercial redistributors to donate.

Users of free software systems can boost the pace of development by
encouraging for-a-fee distributors to donate part of their selling price
to free software developers---the Free Software Foundation, and others.

The way to convince distributors to do this is to demand it and expect
it from them.  So when you compare distributors, judge them partly by
how much they give to free software development.  Show distributors
they must compete to be the one who gives the most.

To make this approach work, you must insist on numbers that you can
compare, such as, ``We will donate ten dollars to the Frobnitz project
for each disk sold.''  Don't be satisfied with a vague promise, such as
``A portion of the profits are donated,'' since it doesn't give a basis
for comparison.

Even a precise fraction ``of the profits from this disk'' is not very
meaningful, since creative accounting and unrelated business decisions
can greatly alter what fraction of the sales price counts as profit.
If the price you pay is $50, ten percent of the profit is probably
less than a dollar; it might be a few cents, or nothing at all.

Some redistributors do development work themselves.  This is useful too;
but to keep everyone honest, you need to inquire how much they do, and
what kind.  Some kinds of development make much more long-term
difference than others.  For example, maintaining a separate version of
a program contributes very little; maintaining the standard version of a
program for the whole community contributes much.  Easy new ports
contribute little, since someone else would surely do them; difficult
ports such as adding a new CPU to the GNU C compiler contribute more;
major new features or packages contribute the most.

By establishing the idea that supporting further development is ``the
proper thing to do'' when distributing free software for a fee, we can
assure a steady flow of resources into making more free software.

@display
Copyright (C) 1994 Free Software Foundation, Inc.
Verbatim copying and redistribution of this section is permitted
without royalty; alteration is not permitted.
@end display

@node Funding GNU Fortran
@chapter Funding GNU Fortran
@cindex funding improvements
@cindex improvements, funding

Work on GNU Fortran is still being done mostly by its author,
James Craig Burley (@email{@value{email-burley}}), who is a volunteer
for, not an employee of, the Free Software Foundation (FSF).
(He has a web page at @uref{@value{www-burley}}.)

As with other GNU software, funding is important because it can pay for
needed equipment, personnel, and so on.

@cindex FSF, funding the
@cindex funding the FSF
The FSF provides information on the best way to fund ongoing
development of GNU software (such as GNU Fortran) in documents
such as the ``GNUS Bulletin''.
Email @email{gnu@@gnu.org} for information on funding the FSF.

To fund specific GNU Fortran work in particular, the FSF might
provide a means for that, but the FSF does not provide direct funding
to the author of GNU Fortran to continue his work.  The FSF has
employee salary restrictions that can be incompatible with the
financial needs of some volunteers, who therefore choose to
remain volunteers and thus be able to be free to do contract work
and otherwise make their own schedules for doing GNU work.

Still, funding the FSF at least indirectly benefits work
on specific projects like GNU Fortran because it ensures the
continuing operation of the FSF offices, their workstations, their
network connections, and so on, which are invaluable to volunteers.
(Similarly, hiring Cygnus Support can help a project like GNU
Fortran---Cygnus has been a long-time donor of equipment usage to the author
of GNU Fortran, and this too has been invaluable---see @ref{Contributors}.)

Currently, the only way to directly fund the author of GNU Fortran
in his work on that project is to hire him for the work you want
him to do, or donate money to him.
Several people have done this
already, with the result that he has not needed to immediately find
contract work on a few occasions.
If more people did this, he
would be able to plan on not doing contract work for many months and
could thus devote that time to work on projects (such as the planned
changes for 0.6) that require longer timeframes to complete.
For the latest information on the status of the author, do
@kbd{finger -l burley@@gnu.org} on a UNIX system
(or any system with a command like UNIX @code{finger}).

Another important way to support work on GNU Fortran is to volunteer
to help out.
Work is needed on documentation, testing, porting
to various machines, and in some cases, coding (although major
changes planned for version 0.6 make it difficult to add manpower to this
area).
Email @email{@value{email-general}} to volunteer for this work.

@xref{Funding,,Funding Free Software}, for more information.

@node Look and Feel
@chapter Protect Your Freedom---Fight ``Look And Feel''
@c the above chapter heading overflows onto the next line. --mew 1/26/93

To preserve the ability to write free software, including replacements
for proprietary software, authors must be free to replicate the
user interface to which users of existing software have become
accustomed.

@xref{Look and Feel,,Protect Your Freedom---Fight ``Look And Feel'',
gcc,Using and Porting GNU CC}, for more information.

@node Getting Started
@chapter Getting Started
@cindex getting started
@cindex new users
@cindex newbies
@cindex beginners

If you don't need help getting started reading the portions
of this manual that are most important to you, you should skip
this portion of the manual.

If you are new to compilers, especially Fortran compilers, or
new to how compilers are structured under UNIX and UNIX-like
systems, you'll want to see @ref{What is GNU Fortran?}.

If you are new to GNU compilers, or have used only one GNU
compiler in the past and not had to delve into how it lets
you manage various versions and configurations of @code{gcc},
you should see @ref{G77 and GCC}.

Everyone except experienced @code{g77} users should
see @ref{Invoking G77}.

If you're acquainted with previous versions of @code{g77},
you should see @ref{News,,News About GNU Fortran}.
Further, if you've actually used previous versions of @code{g77},
especially if you've written or modified Fortran code to
be compiled by previous versions of @code{g77}, you
should see @ref{Changes}.

If you intend to write or otherwise compile code that is
not already strictly conforming ANSI FORTRAN 77---and this
is probably everyone---you should see @ref{Language}.

If you don't already have @code{g77} installed on your
system, you must see @ref{Installation}.

If you run into trouble getting Fortran code to compile,
link, run, or work properly, you might find answers
if you see @ref{Debugging and Interfacing},
see @ref{Collected Fortran Wisdom},
and see @ref{Trouble}.
You might also find that the problems you are encountering
are bugs in @code{g77}---see @ref{Bugs}, for information on
reporting them, after reading the other material.

If you need further help with @code{g77}, or with
freely redistributable software in general,
see @ref{Service}.

If you would like to help the @code{g77} project,
see @ref{Funding GNU Fortran}, for information on
helping financially, and see @ref{Projects}, for information
on helping in other ways.

If you're generally curious about the future of
@code{g77}, see @ref{Projects}.
If you're curious about its past,
see @ref{Contributors},
and see @ref{Funding GNU Fortran}.

To see a few of the questions maintainers of @code{g77} have,
and that you might be able to answer,
see @ref{Open Questions}.

@ifset USING
@node What is GNU Fortran?
@chapter What is GNU Fortran?
@cindex concepts, basic
@cindex basic concepts

GNU Fortran, or @code{g77}, is designed initially as a free replacement
for, or alternative to, the UNIX @code{f77} command.
(Similarly, @code{gcc} is designed as a replacement
for the UNIX @code{cc} command.)

@code{g77} also is designed to fit in well with the other
fine GNU compilers and tools.

Sometimes these design goals conflict---in such cases, resolution
often is made in favor of fitting in well with Project GNU.
These cases are usually identified in the appropriate
sections of this manual.

@cindex compilers
As compilers, @code{g77}, @code{gcc}, and @code{f77}
share the following characteristics:

@itemize @bullet
@cindex source code
@cindex file, source
@cindex code, source
@cindex source file
@item
They read a user's program, stored in a file and
containing instructions written in the appropriate
language (Fortran, C, and so on).
This file contains @dfn{source code}.