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(autoconf.info)Makefile Substitutions

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Substitutions in Makefiles
==========================

   Each subdirectory in a distribution that contains something to be
compiled or installed should come with a file `Makefile.in', from which
`configure' will create a `Makefile' in that directory.  To create a
`Makefile', `configure' performs a simple variable substitution,
replacing occurrences of `@VARIABLE@' in `Makefile.in' with the value
that `configure' has determined for that variable.  Variables that are
substituted into output files in this way are called "output
variables".  They are ordinary shell variables that are set in
`configure'.  To make `configure' substitute a particular variable into
the output files, the macro `AC_SUBST' must be called with that
variable name as an argument.  Any occurrences of `@VARIABLE@' for
other variables are left unchanged.  Note: Setting Output Variables,
for more information on creating output variables with `AC_SUBST'.

   A software package that uses a `configure' script should be
distributed with a file `Makefile.in', but no `Makefile'; that way, the
user has to properly configure the package for the local system before
compiling it.

   Note: Makefile Conventions, for
more information on what to put in `Makefile's.

Preset Output Variables

Output variables that are always set.

Build Directories

Supporting multiple concurrent compiles.

Automatic Remaking

Makefile rules for configuring.