File: autoconf.info,  Node: System Types,  Next: Sharing Defaults,  Prev: Optional Features,  Up: Running configure Scripts

16.6 Specifying a System Type
=============================

By default ‘configure’ builds for the current system.  To create
binaries that can run on a different system type, specify a
‘--host=TYPE’ option along with compiler variables that specify how to
generate object code for TYPE.  For example, to create binaries intended
to run on a 64-bit ARM processor:

     ./configure --host=aarch64-linux-gnu \
        CC=aarch64-linux-gnu-gcc \
        CXX=aarch64-linux-gnu-g++

If done on a machine that can execute these binaries (e.g., via
‘qemu-aarch64’, ‘$QEMU_LD_PREFIX’, and Linux's ‘binfmt_misc’
capability), the build behaves like a native build.  Otherwise it is a
cross-build: ‘configure’ will make cross-compilation guesses instead of
running test programs, and ‘make check’ will not work.

   A system type can either be a short name like ‘mingw64’, or a
canonical name like ‘x86_64-pc-linux-gnu’.  Canonical names have the
form CPU-COMPANY-SYSTEM where SYSTEM is either OS or KERNEL-OS.  To
canonicalize and validate a system type, you can run the command
‘config.sub’, which is often squirreled away in a subdirectory like
‘build-aux’.  For example:

     $ build-aux/config.sub arm64-linux
     aarch64-unknown-linux-gnu
     $ build-aux/config.sub riscv-lnx
     Invalid configuration 'riscv-lnx': OS 'lnx' not recognized

You can look at the ‘config.sub’ file to see which types are recognized.
If the file is absent, this package does not need the system type.

   If ‘configure’ fails with the diagnostic "cannot guess build type".
‘config.sub’ did not recognize your system's type.  In this case, first
fetch the newest versions of these files from the GNU config package
(https://savannah.gnu.org/projects/config).  If that fixes things,
please report it to the maintainers of the package containing
‘configure’.  Otherwise, you can try the configure option ‘--build=TYPE’
where TYPE comes close to your system type; also, please report the
problem to .

   For more details about configuring system types, see *note Manual
Configuration::.