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(autoconf.info)Specifying Names


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Specifying the System Type
==========================

   Like other GNU `configure' scripts, Autoconf-generated `configure'
scripts can make decisions based on a canonical name for the system
type, which has the form:

     CPU-COMPANY-SYSTEM

   `configure' can usually guess the canonical name for the type of
system it's running on.  To do so it runs a script called
`config.guess', which derives the name using the `uname' command or
symbols predefined by the C preprocessor.

   Alternately, the user can specify the system type with command line
arguments to `configure'.  Doing so is necessary when cross-compiling.
In the most complex case of cross-compiling, three system types are
involved.  The options to specify them are:

`--build=BUILD-TYPE'
     the type of system on which the package is being configured and
     compiled (rarely needed);

`--host=HOST-TYPE'
     the type of system on which the package will run;

`--target=TARGET-TYPE'
     the type of system for which any compiler tools in the package will
     produce code.

If the user gives `configure' a non-option argument, it is used as the
default for the host, target, and build system types if the user does
not specify them explicitly with options.  The target and build types
default to the host type if it is given and they are not.  If you are
cross-compiling, you still have to specify the names of the cross-tools
you use, in particular the C compiler, on the `configure' command line,
e.g.,

     CC=m68k-coff-gcc configure --target=m68k-coff

   `configure' recognizes short aliases for many system types; for
example, `decstation' can be given on the command line instead of
`mips-dec-ultrix4.2'.  `configure' runs a script called `config.sub' to
canonicalize system type aliases.


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