Autoconf-generated configure scripts can make decisions based on a canonical name for the system type, or target triplet, 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
command or symbols predefined by the C preprocessor.
Alternately, the user can specify the system type with command line arguments to configure (see System Type. 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:
If you mean to override the result of config.guess, use --build, not --host, since the latter enables cross-compilation. For historical reasons, whenever you specify --host, be sure to specify --build too; this will be fixed in the future. So, to enter cross-compilation mode, use a command like this
./configure --build=i686-pc-linux-gnu --host=m68k-coff
Note that if you do not specify --host, configure fails if it can't run the code generated by the specified compiler. For example, configuring as follows fails:
When cross-compiling, configure will warn about any tools (compilers, linkers, assemblers) whose name is not prefixed with the host type. This is an aid to users performing cross-compilation. Continuing the example above, if a cross-compiler named cc is used with a native pkg-config, then libraries found by pkg-config will likely cause subtle build failures; but using the names m68k-coff-cc and m68k-coff-pkg-config avoids any confusion. Avoiding the warning is as simple as creating the correct symlinks naming the cross tools.
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 Hosts and Cross-Compilation.