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:
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.
is passed directly to cpp. It is typically used to indicate the directory in which the imake template and configuration files may be found.
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. -ffilename
specifies the name of the per-directory input file. The default is Imakefile.
specifies the name of the .c file that is constructed in the current directory. The default is Imakefile.c.
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.
indicates that imake should execute the generated Makefile. The default is to leave this to the user.
indicates that imake should print the cpp command line that it is using to generate the Makefile.
imake invokes cpp with any
#define IMAKE_TEMPLATE "Imake.tmpl" #define INCLUDE_IMAKEFILE <Imakefile> #include IMAKE_TEMPLATE
where Imake.tmpl and Imakefile may be overridden
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. You can create such variables 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
When building X programs outside the source tree, a special symbol UseInstalled is defined and TOPDIR and CURDIR are omitted. If the configuration files have been properly installed, the script xmkmf may be used.
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.
temporary input file for cpp
temporary Makefile for
temporary Imakefile if specified Imakefile uses # comments
default C preprocessor
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:
If defined, this specifies a
-Iinclude argument to pass to the C preprocessor. For example, -I/usr/X11/config.
If defined, this should be a valid path to a preprocessor program. For example, /usr/local/cpp. By default, imake will use /lib/cpp.
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(). This variable is only used if the -eoption is specified.
Todd Brunhoff, Tektronix and MIT Project Athena; Jim Fulton, MIT X Consortium
All UNIX systems. Windows Server 2012. Windows 8.1. Windows Server 2012 R2. Windows 10. Windows Server 2016. Windows Server 2019.
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