configure.texi

早期freebsd实现

@defvar{subdirs}
Contains the names of any subdirectories where @code{configure} should
create a @code{Makefile} (in addition to the current directory),
@emph{without} recursively running @code{configure}.
Use @code{subdirs} (instead of the @code{configdirs} variable
described above) if you want to configure all of the directories
as a unit.  Since there is a single invocation of @code{configure}
that configures many directories, all the directories can use the
same Makefile fragments, and the same @code{configure.in}.
@end defvar

@defvar{host}
Contains the full configuration name (generated by the script
@file{config.sub} from the name that the user entered) for the host.
This is a three-part name of the form 

@example
@var{cpu}-@var{vendor}-@var{os}
@end example

@noindent
There are separate variables @code{host_cpu}, @code{host_vendor}, and
@code{host_os} that you can use to test each of the three parts; this
variable is useful, however, for error messages, and for testing
combinations of the three components.
@end defvar

@defvar{host_cpu}
Contains the first element of the canonical triple representing the host
as returned by @file{config.sub}.  This is occasionally used to
distinguish between minor variations of a particular vendor's operating
system and sometimes to determine variations in binary format between
the host and the target.
@end defvar

@defvar{host_vendor}
Contains the second element of the canonical triple representing the
host as returned by @file{config.sub}.  This is usually used to
distinguish betwen the numerous variations between @emph{common}
operating systems.
@c "@emph{common} OS" doesn't convey much to me.  Is this meant to cover 
@c cases like Unix, widespread but with many variations?
@end defvar

@defvar{host_os}
Contains the the third element of the canonical triple representing the
host as returned by @file{config.sub}.
@end defvar

@defvar{target}
Contains the full configuration name (generated by the script
@file{config.sub} from the name that the user entered) for the target.
This is a three-part name of the form 

@example
@var{cpu}-@var{vendor}-@var{os}
@end example

@noindent
There are separate variables @code{target_cpu}, @code{target_vendor}, and
@code{target_os} that you can use to test each of the three parts; this
variable is useful, however, for error messages, and for testing
combinations of the three components.
@end defvar

@defvar{target_cpu}
Contains the first element of the canonical triple representing the
target as returned by @file{config.sub}.  This is used heavily by
programs involved in building programs, like the compiler, assembler,
linker, etc.  Most programs will not need the @code{target} variables at
all, but this one could conceivably be used to build a program, for
instance, that operated on binary data files whose byte order or
alignment differ from the system where the program is running.
@end defvar

@defvar{target_vendor}
Contains the second element of the canonical triple representing the
target as returned by @file{config.sub}.  This is usually used to
distinguish betwen the numerous variations between @emph{common}
operating systems or object file formats.  Sometimes it is used to
switch between different flavors of user interfaces.
@c above query re "@emph{common} OS" applies here too
@end defvar

@defvar{target_os}
Contains the the third element of the canonical triple representing the
target as returned by @file{config.sub}.  This variable is used by
development tools to distinguish between subtle variations in object
file formats that some vendors use across operating system releases.  It
might also be use to decide which libraries to build or what user
interface the tool should provide.
@end defvar

@defvar{floating_point}
Is set to @code{no} if the user invoked configure with the @code{-nfp}
command line option, otherwise it is empty.  This is a request to target
machines with @emph{no floating point} unit, even if the targets
ordinarily have floating point units available.  This option has no
negation.
@end defvar

@defvar{gas}
Is set to @code{true} if the user invoked configure with the @code{-gas}
command line option, otherwise it is empty.  This is a request to assume
that all target machines have @sc{gas} available even if they ordinarily do
not.  The converse option @samp{-no-gas} is not available.
@end defvar

@defvar{x}
Is set to @code{true} if the user invoked configure with the @code{-x}
command line option, otherwise it is empty.  This is a request to assume
that @sc{mit x11} compatible headers files and libraries are available
on all hosts, regardless of what is normally available on them.
@end defvar

@defvar{srcdir}
Is set to the name of the directory containing the source for this
program.  This will be different from @file{.} if the user has specified
the @code{-srcdir=} option.  Note that @code{srcdir} is not necessarily
an absolute path.
@end defvar

@defvar{host_makefile_frag}
If set by @file{configure.in}, this variable should be the name a file,
relative to @code{srcdir} to be included in the resulting Makefile.  If
the named file does not exist, @code{configure} will print a warning
message.  This variable is not set by @code{configure}.
@end defvar

@defvar{target_makefile_frag}
If set by @file{configure.in}, this variable should be the name of a
file, relative to @code{srcdir}, to be included in the resulting
Makefile.  If the named file does not exist, @code{configure} will print
a warning message.  This variable is not set by @code{configure}.
@end defvar

@defvar{site_makefile_frag} 
Is set to a file name representing to the default Makefile fragment for
this host.  It may be set in @file{configure.in} to override this
default.  Normally @code{site_makefile_frag} is empty, but will have a
value if the user specified @code{-site=} on the command line.  It is
probably not a good idea to override this variable from
@file{configure.in}, since that may defeat the @code{configure} user's
intentions. 
@end defvar

@defvar{Makefile}
Is set to the name of the generated @file{Makefile}.  Normally this
value is precisely @file{Makefile} but some programs may want something
else.
@end defvar

@defvar{removing}
Is normally empty but will be set to some non-empty value if the user
specified @code{-rm} on the command line.  That is, if @code{removing}
is non-empty, then configure is @emph{removing} a configuration rather
than creating one.
@end defvar

@defvar{files}
If this variable is non-empty following the @code{per-target:} section,
then each word in its value will be the target of a symbolic link named
in the corresponding word from the @code{links} variable.
@end defvar

@defvar{links}
If the @code{files} variable is non-empty following the
@code{per-target:} section, then @code{configure} creates symbolic links
with the first word of @code{links} pointing to the first word of
@code{files}, the second word of @code{links} pointing to the second
word of @code{files}, and so on.
@end defvar

@node Declarations, Per-host, Configure Variables, configure.in
@subsection For each invocation

@cindex Declarations section

@code{configure} sources the entire shell script fragment from the start
of @file{configure.in} up to a line beginning with @samp{# Per-host:}
immediately after parsing command line arguments.  The variables
@code{srctrigger} and @code{srcname} @emph{must} be set here.

You might also want to set the variable @code{configdirs} here.

@node Per-host, Per-target, Declarations, configure.in
@subsection For each host
@cindex per-host section
@cindex host shell-script fragment

The per-host section of @file{configure.in} starts with the line that begins
with @samp{# Per-host:} and ends before a line beginning with 
@samp{# Per-target:}.  @code{configure} sources the per-host section once for
each host.

This section usually contains a big case statement using the variables
@samp{host_cpu}, @samp{host_vendor}, and @samp{host_os} to determine
appropriate values for @samp{host_makefile_frag} and @samp{files},
although @samp{files} is not usually set here.  Usually, it is set
at the end of the per-target section after determining the names of the
target specific configuration files.

@node Per-target, Post-target, Per-host, configure.in
@subsection For each target
@cindex per-target section
@cindex target shell-script fragment

The per-target section of @file{configure.in} starts with the line that
begins with @samp{# Per-target:} and ends before the line that begins
with @samp{# Post-target:}, if there is such a line.  Otherwise the
per-target section extends to the end of the file.  @code{configure} sources
the per-target section once for each target before building any files,
directories, or links.

This section usually contains a big case statement using the variables called
@samp{target_cpu}, @samp{target_vendor}, and @samp{target_os} to determine
appropriate values for @samp{target_makefile_frag} and @samp{files}.
The last lines in the per-target section normally set the variables
@code{files} and @code{links}.

@node Post-target, Example, Per-target, configure.in
@subsection After each target

The post-target section is optional.  If it exists, the post-target
section starts with a line beginning with @code{# Post-target:} and
extends to the end of the file.  If it exists, @code{configure} sources this
section once for each target after building all files, directories, or
links.

This section is seldom needed, but you can use it to edit the Makefile
generated by @code{configure}.

@node Example,  , Post-target, configure.in
@subsection An example @file{configure.in}
@cindex example @file{configure.in}
@cindex sample @file{configure.in}
@cindex Bison @file{configure.in}

Here is a small example of a @file{configure.in} file.

@example
# This file is a collection of shell script fragments used to tailor
# a template configure script as appropriate for this directory.  
# For more information, see configure.texi.

configdirs=
srctrigger=warshall.c
srcname="bison"

# per-host:
case "$@{host_os@}" in
m88kbcs)
	host_makefile_frag=config/mh-delta88
	;;
esac

# per-target:

files="bison_in.hairy"
links="bison.hairy"

# post-target:
@end example

@node config.status, Makefile Fragments, configure.in, Reference
@section @code{config.status}

@kindex config.status

The final step in configuring a directory is to create an executable
shell script, @file{config.status}.  The main purpose of this file
is to allow the Makefile for the current directory to rebuild itself, if
necessary.  For this reason, @file{config.status} uses the
@samp{-norecursion} option to @code{configure}, and is therefore
probably inappropriate for reconfiguring a tree of source code.

@node Makefile Fragments,  , config.status, Reference
@section Makefile Fragments

@cindex Makefile fragments

Cygnus @code{configure} uses three types of Makefile fragments.  In a
generated Makefile they appear in the order target fragment, host
fragment, and site fragment.  This allows host fragments to override
target fragments, and site fragments to override both.

Host specific Makefile fragments conventionally reside in the
@file{./config} directory with names of the form
@file{mh-@var{host}}.  They are used for hosts that require
odd options to the standard compiler and for compile time options based
on the host configuration.

Target specific Makefile fragments conventionally reside in the
@file{./config} directory with names of the form @file{mt-@var{target}}.
They are used for target dependent compile time options.

Site specific Makefile fragments conventionally reside in the
@file{./config} directory with names of the form @file{ms-@var{site}}.
They are used to override host and target independent compile time
options.  Note that you can also override these options on the
@code{make} invocation line.

@node Known Bugs, Variables Index, Reference, top
@chapter Known Bugs

@cindex bugs

We know of the following bugs:

@itemize @bullet

@item
There is no way to query about known hosts, known targets, or the
porting or testing status of any configuration.

@item
The negations to the options @code{-gas}, @code{-x}, and @code{-nfp} are
not available.

@end itemize

@page
@node Variables Index, Concept Index, Known Bugs, top
@appendix Variable Index

@printindex vr

@page
@node     Concept Index,  , Variables Index, top
@appendix Concept Index

@printindex cp
@contents
@bye

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