A GNU configuration name has three parts: the CPU type, the manufacturer's name, and the operating system. `configure' uses these to pick the list of system-dependent directories to look for. If the `--nfp' option is not passed to `configure', the directory `machine/fpu' is also used. The operating system often has a base operating system; for example, if the operating system is `sunos4.1', the base operating system is `unix/bsd'. The algorithm used to pick the list of directories is simple: `configure' makes a list of the base operating system, manufacturer, CPU type, and operating system, in that order. It then concatenates all these together with slashes in between, to produce a directory name; for example, the configuration `sparc-sun-sunos4.1' results in `unix/bsd/sun/sparc/sunos4.1'. `configure' then tries removing each element of the list in turn, so `unix/bsd/sparc' and `sun/sparc' are also tried, among others. Since the precise version number of the operating system is often not important, and it would be very inconvenient, for example, to have identical `sunos4.1.1' and `sunos4.1.2' directories, `configure' tries successively less specific operating system names by removing trailing suffixes starting with a period.
As an example, here is the complete list of directories that would be tried for the configuration `sparc-sun-sunos4.1' (without the `--nfp' option):
sparc/fpu unix/bsd/sun/sunos4.1/sparc unix/bsd/sun/sunos4.1 unix/bsd/sun/sunos4/sparc unix/bsd/sun/sunos4 unix/bsd/sun/sunos/sparc unix/bsd/sun/sunos unix/bsd/sun/sparc unix/bsd/sun unix/bsd/sunos4.1/sparc unix/bsd/sunos4.1 unix/bsd/sunos4/sparc unix/bsd/sunos4 unix/bsd/sunos/sparc unix/bsd/sunos unix/bsd/sparc unix/bsd unix/sun/sunos4.1/sparc unix/sun/sunos4.1 unix/sun/sunos4/sparc unix/sun/sunos4 unix/sun/sunos/sparc unix/sun/sunos unix/sun/sparc unix/sun unix/sunos4.1/sparc unix/sunos4.1 unix/sunos4/sparc unix/sunos4 unix/sunos/sparc unix/sunos unix/sparc unix sun/sunos4.1/sparc sun/sunos4.1 sun/sunos4/sparc sun/sunos4 sun/sunos/sparc sun/sunos sun/sparc sun sunos4.1/sparc sunos4.1 sunos4/sparc sunos4 sunos/sparc sunos sparc
Different machine architectures are conventionally subdirectories at the top level of the `sysdeps' directory tree. For example, `sysdeps/sparc' and `sysdeps/m68k'. These contain files specific to those machine architectures, but not specific to any particular operating system. There might be subdirectories for specializations of those architectures, such as `sysdeps/m68k/68020'. Code which is specific to the floating-point coprocessor used with a particular machine should go in `sysdeps/machine/fpu'.
There are a few directories at the top level of the `sysdeps' hierarchy that are not for particular machine architectures.
floatis IEEE 754 single-precision format, and
doubleis IEEE 754 double-precision format. Usually this directory is referred to in the `Implies' file in a machine architecture-specific directory, such as `m68k/Implies'.
socketand related functions on Unix systems. The `inet' top-level subdirectory is enabled by `unix/inet/Subdirs'. `unix/common' implies `unix/inet'.
Go to the first, previous, next, last section, table of contents.