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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-VENDOR-OS', where OS can be `SYSTEM' or
`KERNEL-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 infers 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.  It defaults to the result of running `config.guess'.

`--host=HOST-TYPE'
     the type of system on which the package will run.  By default it
     is the same as the build machine.  Specifying it enables the
     cross-compilation mode.

`--target=TARGET-TYPE'
     the type of system for which any compiler tools in the package will
     produce code (rarely needed).  By default, it is the same as host.

   If you mean to override the result of `config.guess', use `--build',
not `--host', since the latter enables cross-compilation.  For
historical reasons, passing `--host' also changes the build type.
Therefore, whenever you specify `--host', be sure to specify `--build'
too.  This will be fixed in the future.

     ./configure --build=i686-pc-linux-gnu --host=m68k-coff

will enter cross-compilation mode, but `configure' will fail if it
can't run the code generated by the specified compiler if you configure
as follows:

     ./configure CC=m68k-coff-gcc

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

   This section deliberately omits the description of the obsolete
interface, see Note: Hosts and Cross-Compilation.