g77install.texi

gcc-2.95.3 Linux下最常用的C编译器

(The output also is likely to include a diagnostic from
the linker, since there's no @samp{main_()} function.)
However, you do have to sift through it yourself; @code{gcc}
currently provides no easy way to ask it where it is installed
and where it looks for the various programs and data files it
calls on to do its work.

Just @emph{building} @code{g77} should not overwrite any installed
programs---but, usually, after you build @code{g77}, you will want
to install it, so backing up anything it might overwrite is
a good idea.
(This is true for any package, not just @code{g77},
though in this case it is intentional that @code{g77} overwrites
@code{gcc} if it is already installed---it is unusual that
the installation process for one distribution intentionally
overwrites a program or file installed by another distribution,
although, in this case, @code{g77} is an augmentation of the
@code{gcc} distribution.)

Another reason to back up the existing version first,
or make sure you can restore it easily, is that it might be
an older version on which other users have come to depend
for certain behaviors.
However, even the new version of @code{gcc} you install
will offer users the ability to specify an older version of
the actual compilation programs if desired, and these
older versions need not include any @code{g77} components.
@xref{Target Options,,Specifying Target Machine and Compiler Version,
gcc,Using and Porting GNU CC}, for information on the @samp{-V}
option of @code{gcc}.

@node Configuring gcc
@subsection Configuring GNU CC

@code{g77} is configured automatically when you configure
@code{gcc}.
There are two parts of @code{g77} that are configured in two
different ways---@code{g77}, which ``camps on'' to the
@code{gcc} configuration mechanism, and @code{libg2c}, which
uses a variation of the GNU @code{autoconf} configuration
system.

Generally, you shouldn't have to be concerned with
either @code{g77} or @code{libg2c} configuration, unless
you're configuring @code{g77} as a cross-compiler.
In this case, the @code{libg2c} configuration, and possibly the
@code{g77} and @code{gcc} configurations as well,
might need special attention.
(This also might be the case if you're porting @code{gcc} to
a whole new system---even if it is just a new operating system
on an existing, supported CPU.)

To configure the system, see
@ref{Installation,,Installing GNU CC,gcc,Using and Porting GNU CC},
following the instructions for running @file{./configure}.
Pay special attention to the @samp{--prefix=} option, which
you almost certainly will need to specify.

(Note that @code{gcc} installation information is provided
as a plain-text file in @file{gcc/INSTALL}.)

The information printed by the invocation of @file{./configure}
should show that the @file{f} directory (the Fortran language)
has been configured.
If it does not, there is a problem.

@emph{Note:} Configuring with the @samp{--srcdir} argument,
or by starting in an empty directory
and typing a command such as @kbd{../gcc/configure} to
build with separate build and source directories,
is known to work with GNU @code{make},
but it is known to not work with other variants of @code{make}.
Irix5.2 and SunOS4.1 versions of @code{make} definitely
won't work outside the source directory at present.

@code{g77}'s portion of the @file{configure} script
used to issue a warning message about this
when configuring for building binaries outside the source directory,
but no longer does this as of version 0.5.23.

Instead, @code{g77} simply rejects most common attempts
to build it using a non-GNU @code{make} when the
build directory is not the same as the source directory,
issuing an explanatory diagnostic.

@node Building gcc
@subsection Building GNU CC
@cindex building @code{gcc}
@cindex building @code{g77}

@cindex @code{LANGUAGES} macro
Building @code{g77} requires building enough of @code{gcc} that
these instructions assume you're going to build all of
@code{gcc}, including @code{g++}, @code{protoize}, and so on.
You can save a little time and disk space by changes the
@code{LANGUAGES} macro definition in @code{gcc/Makefile.in}
or @code{gcc/Makefile}, but if you do that, you're on your own.
One change is almost @emph{certainly} going to cause failures:
removing @code{c} or @code{f77} from the definition of the
@code{LANGUAGES} macro.

After configuring @code{gcc}, which configures @code{g77} and
@code{libg2c} automatically, you're ready to start the actual
build by invoking @code{make}.

@pindex configure
@emph{Note:} You @strong{must} have run the @file{configure}
script in @code{gcc} before you run @code{make},
even if you're using an already existing @code{gcc} development directory,
because @file{./configure} does the work to recognize that you've added
@code{g77} to the configuration.

There are two general approaches to building GNU CC from
scratch:

@table @dfn
@item bootstrap
This method uses minimal native system facilities to
build a barebones, unoptimized @code{gcc}, that is then
used to compile (``bootstrap'') the entire system.

@item straight
This method assumes a more complete native system
exists, and uses that just once to build the entire
system.
@end table

On all systems without a recent version of @code{gcc}
already installed, the @i{bootstrap} method must be
used.
In particular, @code{g77} uses extensions to the C
language offered, apparently, only by @code{gcc}.

On most systems with a recent version of @code{gcc}
already installed, the @i{straight} method can be
used.
This is an advantage, because it takes less CPU time
and disk space for the build.
However, it does require that the system have fairly
recent versions of many GNU programs and other
programs, which are not enumerated here.

@menu
* Bootstrap Build::  For all systems.
* Straight Build::   For systems with a recent version of @code{gcc}.
@end menu

@node Bootstrap Build
@subsubsection Bootstrap Build
@cindex bootstrap build
@cindex build, bootstrap

A complete bootstrap build is done by issuing a command
beginning with @samp{make bootstrap @dots{}}, as
described in @ref{Installation,,Installing GNU CC,
gcc,Using and Porting GNU CC}.
This is the most reliable form of build, but it does require
the most disk space and CPU time, since the complete system
is built twice (in Stages 2 and 3), after an initial build
(during Stage 1) of a minimal @code{gcc} compiler using
the native compiler and libraries.

You might have to, or want to, control the way a bootstrap
build is done by entering the @code{make} commands to build
each stage one at a time, as described in the @code{gcc}
manual.
For example, to save time or disk space, you might want
to not bother doing the Stage 3 build, in which case you
are assuming that the @code{gcc} compiler you have built
is basically sound (because you are giving up the opportunity
to compare a large number of object files to ensure they're
identical).

To save some disk space during installation, after Stage 2
is built, you can type @samp{rm -fr stage1} to remove the
binaries built during Stage 1.

Also, see @ref{Installation,,Installing GNU CC,gcc,Using and Porting GNU CC},
for important information on building @code{gcc} that is
not described in this @code{g77} manual.
For example, explanations of diagnostic messages
and whether they're expected, or indicate trouble,
are found there.

@node Straight Build
@subsubsection Straight Build
@cindex straight build
@cindex build, straight

If you have a recent version of @code{gcc}
already installed on your system, and if you're
reasonably certain it produces code that is
object-compatible with the version of @code{gcc}
you want to build as part of building @code{g77},
you can save time and disk space by doing a straight
build.

To build just the compilers along with the
necessary run-time libraries, issue the following
command:

@example
make -k CC=gcc
@end example

If you run into problems using this method, you have
two options:

@itemize @bullet
@item
Abandon this approach and do a bootstrap build.

@item
Try to make this approach work by diagnosing the
problems you're running into and retrying.
@end itemize

Especially if you do the latter, you might consider
submitting any solutions as bug/fix reports.
@xref{Trouble,,Known Causes of Trouble with GNU Fortran}.

However, understand that many problems preventing a
straight build from working are not @code{g77} problems,
and, in such cases, are not likely to be addressed in
future versions of @code{g77}.
Consider treating them as @code{gcc} bugs instead.

@node Pre-installation Checks
@subsection Pre-installation Checks
@cindex pre-installation checks
@cindex installing, checking before

Before installing the system, which includes installing
@code{gcc}, you might want to do some minimum checking
to ensure that some basic things work.

Here are some commands you can try, and output typically
printed by them when they work:

@example
sh# @kbd{cd /usr/src/gcc}
sh# @kbd{./g77 -B./ -v}
g77 version @value{version-g77}
Driving: ./g77 -B./ -v -c -xf77-version /dev/null -xnone
Reading specs from ./specs
gcc version @value{version-gcc}
 cpp -lang-c -v -isystem ./include -undef -D__GNUC__=2 @dots{}
GNU CPP version @value{version-gcc} (Alpha GNU/Linux with ELF)
#include "..." search starts here:
#include <...> search starts here:
 include
 /usr/alpha-linux/include
 /usr/lib/gcc-lib/alpha-linux/@value{version-gcc}/include
 /usr/include
End of search list.
 ./f771 -fnull-version -quiet -dumpbase g77-version.f -version @dots{}
GNU F77 version @value{version-gcc} (alpha-linux) compiled @dots{}
GNU Fortran Front End version @value{version-g77}
 as -nocpp -o /tmp/cca14485.o /tmp/cca14485.s
 ld -m elf64alpha -G 8 -O1 -dynamic-linker /lib/ld-linux.so.2 @dots{}
 /tmp/cca14485
__G77_LIBF77_VERSION__: @value{version-g77}
@@(#)LIBF77 VERSION 19970919
__G77_LIBI77_VERSION__: @value{version-g77}
@@(#) LIBI77 VERSION pjw,dmg-mods 19980405
__G77_LIBU77_VERSION__: @value{version-g77}
@@(#) LIBU77 VERSION 19970919
sh# @kbd{./xgcc -B./ -v -o /tmp/delete-me -xc /dev/null -xnone}
Reading specs from ./specs
gcc version @value{version-gcc}
 ./cpp -lang-c -v -isystem ./include -undef @dots{}
GNU CPP version @value{version-gcc} (Alpha GNU/Linux with ELF)
#include "..." search starts here:
#include <...> search starts here:
 include
 /usr/alpha-linux/include
 /usr/lib/gcc-lib/alpha-linux/@value{version-gcc}/include
 /usr/include
End of search list.
 ./cc1 /tmp/cca18063.i -quiet -dumpbase null.c -version @dots{}
GNU C version @value{version-gcc} (alpha-linux) compiled @dots{}
 as -nocpp -o /tmp/cca180631.o /tmp/cca18063.s
 ld -m elf64alpha -G 8 -O1 -dynamic-linker /lib/ld-linux.so.2 @dots{}
/usr/lib/crt1.o: In function `_start':
../sysdeps/alpha/elf/start.S:77: undefined reference to `main'
../sysdeps/alpha/elf/start.S:77: undefined reference to `main'
sh#
@end example

(Note that long lines have been truncated, and @samp{@dots{}}
used to indicate such truncations.)

The above two commands test whether @code{g77} and @code{gcc},
respectively, are able to compile empty (null) source files,
whether invocation of the C preprocessor works, whether libraries
can be linked, and so on.

If the output you get from either of the above two commands
is noticeably different, especially if it is shorter or longer
in ways that do not look consistent with the above sample
output, you probably should not install @code{gcc} and @code{g77}
until you have investigated further.

For example, you could try compiling actual applications and
seeing how that works.
(You might want to do that anyway, even if the above tests
work.)

To compile using the not-yet-installed versions of @code{gcc}
and @code{g77}, use the following commands to invoke them.

To invoke @code{g77}, type:

@example
/usr/src/gcc/g77 -B/usr/src/gcc/ @dots{}
@end example

To invoke @code{gcc}, type:

@example
/usr/src/gcc/xgcc -B/usr/src/gcc/ @dots{}
@end example

@node Installation of Binaries
@subsection Installation of Binaries
@cindex installation of binaries
@cindex @code{g77}, installation of
@cindex @code{gcc}, installation of

After configuring, building, and testing @code{g77} and @code{gcc},
when you are ready to install them on your system, type:

@example
make -k CC=gcc install
@end example

As described in @ref{Installation,,Installing GNU CC,
gcc,Using and Porting GNU CC}, the values for
the @code{CC} and @code{LANGUAGES} macros should
be the same as those you supplied for the build
itself.

So, the details of the above command might vary
if you used a bootstrap build (where you might be
able to omit both definitions, or might have to
supply the same definitions you used when building
the final stage) or if you deviated from the
instructions for a straight build.

If the above command does not install @file{libg2c.a}
as expected, try this:

@example
make -k @dots{} install install-libf77
@end example

We don't know why some non-GNU versions of @code{make} sometimes
require this alternate command, but they do.
(Remember to supply the appropriate definition for @code{CC}
where you see @samp{@dots