imake - C preprocessor interface to the make utility

imake [ -Ddefine ] [ -Idir ] [ -Udefine ] [ -Ttemplate ] [ -f filename ] [ -C filename ] [ -s filename ] [ -e ] [ -v ]

Imake is used to generate Makefiles from a template, a set of cpp macro functions, and a per-directory input file called an Imakefile. This allows machine dependencies (such as compiler options, alternate command names, and special make rules) to be kept separate from the descriptions of the various items to be built.

The following command line options may be passed to imake:

-Ddefine

This option is passed directly to cpp. It is typically used to set directory-specific variables. For example, the X Window System uses this flag to set TOPDIR to the name of the directory containing the top of the core distribution and CURDIR to the name of the current directory, relative to the top.

-Idirectory

This option is passed directly to cpp. It is typically used to indicate the directory in which the imake template and configuration files may be found.

-Udefine

This option is passed directly to cpp. It is typically used to unset variables when debugging imake configuration files.

-Ttemplate

This option specifies the name of the master template file (which is usually located in the directory specified with -I) used by cpp. The default is Imake.tmpl.

-f filename

This option specifies the name of the per-directory input file. The default is Imakefile.

-C filename

This option specifies the name of the .c file that is constructed in the current directory. The default is Imakefile.c.

-s filename

This option specifies the name of the make description file to be generated but make should not be invoked. If the filename is a dash (-), the output is written to stdout. The default is to generate, but not execute, a Makefile.

-e

This option indicates the imake should execute the generated Makefile. The default is to leave this to the user.

-v

This option indicates that imake should print the cpp command line that it is using to generate the Makefile.

Imake invokes cpp with any -I or -D flags passed on the command line and passes the name of a file containing the following 3 lines:

		#define IMAKE_TEMPLATE "Imake.tmpl"
		#define INCLUDE_IMAKEFILE <Imakefile>
		#include IMAKE_TEMPLATE

The IMAKE_TEMPLATE typically reads in a file containing machine-dependent parameters (specified as cpp symbols), a site-specific parameters file, a file defining variables, a file containing cpp macro functions for generating make rules, and finally the Imakefile (specified by INCLUDE_IMAKEFILE) in the current directory. The Imakefile uses the macro functions to indicate what targets should be built; imake takes care of generating the appropriate rules.

Imake configuration files contain two types of variables, imake variables and make variables. The imake variables are interpreted by cpp when imake is run. By convention they are mixed case. The make variables are written into the Makefile for later interpretation by make. By convention make variables are upper case.

The rules file (usually named Imake.rules in the configuration directory) contains a variety of cpp macro functions that are configured according to the current platform. Imake replaces any occurrences of the string ``@@'' with a newline to allow macros that generate more than one line of make rules. For example, the macro

#define program_target(program, objlist) @@\ program: objlist @@\ $(CC) -o $@ objlist $(LDFLAGS)

when called with program_target(foo, foo1.o foo2.o) will expand to

foo: foo1.o foo2.o $(CC) -o $@ foo1.o foo2.o $(LDFLAGS)

Imake also replaces any occurrences of the word ``XCOMM'' with the character ``#'' to permit placing comments in the Makefile without causing ``invalid directive'' errors from the preprocessor.

Some complex imake macros require generated make variables local to each invocation of the macro, often because their value depends on parameters passed to the macro. Such variables can be created by using an imake variable of the form XVARdefn, where n is a single digit. A unique make variable will be substituted. Later occurrences of the variable XVARusen will be replaced by the variable created by the corresponding XVARdefn.

On systems whose cpp reduces multiple tabs and spaces to a single space, imake attempts to put back any necessary tabs (make is very picky about the difference between tabs and spaces). For this reason, colons (:) in command lines must be preceded by a backslash (\).

The X Window System uses imake extensively, for both full builds within the source tree and external software. As mentioned above, two special variables, TOPDIR and CURDIR, are set to make referencing files using relative path names easier. For example, the following command is generated automatically to build the Makefile in the directory lib/X/ (relative to the top of the sources):

	%  ../.././config/imake  -I../.././config  \
		-DTOPDIR=../../.   -DCURDIR=./lib/X

Here is a summary of the files read by imake as used by X. The indentation shows what files include what other files.

    Imake.tmpl	generic variables
        site.def	site-specific, BeforeVendorCF defined
        *.cf	machine-specific
            *Lib.rules	shared library rules
        site.def	site-specific, AfterVendorCF defined
        Imake.rules	rules
        Project.tmpl	X-specific variables
            *Lib.tmpl	shared library variables
        Imakefile
            Library.tmpl	library rules
            Server.tmpl	server rules
            Threads.tmpl	multi-threaded rules

Note that site.def gets included twice, once before the *.cf file and once after. Although most site customizations should be specified after the *.cf file, some, such as the choice of compiler, need to be specified before, because other variable settings may depend on them.

The first time site.def is included, the variable BeforeVendorCF is defined, and the second time, the variable AfterVendorCF is defined. All code in site.def should be inside an #ifdef for one of these symbols.

Imakefile.c temporary input file for cpp

/tmp/Imf.XXXXXX temporary Makefile for -s

/tmp/IIf.XXXXXX temporary Imakefile if specified Imakefile uses # comments

/usr/bin/cpp default C preprocessor

make(1), xmkmf(1)

S. I. Feldman, Make - A Program for Maintaining Computer Programs

The following environment variables may be set, however their use is not recommended as they introduce dependencies that are not readily apparent when imake is run:

IMAKEINCLUDE

If defined, this specifies a ``-I'' include argument to pass to the C preprocessor. E.g., ``-I/usr/X11/config''.

IMAKECPP

If defined, this should be a valid path to a preprocessor program. E.g., ``/usr/local/cpp''. By default, imake will use cc -E or /usr/bin/cpp, depending on the OS specific configuration.

IMAKEMAKE

If defined, this should be a valid path to a make program, such as ``/usr/local/make''. By default, imake will use whatever make program is found using execvp(3). This variable is only used if the ``-e'' option is specified.

Todd Brunhoff, Tektronix and MIT Project Athena; Jim Fulton, MIT X Consortium