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#  $Id: README,v 1.2 2001-09-27 12:02:50 chris Exp $
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#
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    make/README
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    This file describes the layout and conventions of the application
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    makefile support for RTEMS applications.  Internally, RTEMS uses
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    GNU-style autoconf/automake Makefiles as much as possible to
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    ease integration with other GNU tools.
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    All of these "make" trees are substantially similar; however this
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    file documents the current state of the RTEMS Application Makefile
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    support.
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    This make tree is based on a build system originally developed
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    to simplify porting projects between various OS's.  The primary
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    goals were:
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        .  simple *and* customizable individual makefiles
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        .  use widely available GNU make.  There is no pre-processing or
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            automatic generation of Makefiles.
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        .  Same makefiles work on *many* host OS's due to portability
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            of GNU make and the host OS config files.
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        .  Support for different compilers and operating systems
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            on a per-user basis.  Using the same sources (including
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            Makefiles) one developer can develop and test under SVR4,
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            another under 4.x, another under HPUX.
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        .  Builtin support for compiling "variants" such as debug,
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            profile, and tcov versions.  These variants can be built
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            recursively.
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        .  Control of system dependencies.  "hidden" dependencies on
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            environment variables (such as PATH)
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            have been removed whenever possible.  No matter what your
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            PATH variable is set to, you should get the same thing
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            when you 'make' as everyone else on the project.
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    This Makefile system has evolved into its present form and as it
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    exists in RTEMS today, its sole goal is to build RTEMS applications.
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    The use of these Makefiles hides the complexity of producing
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    executables for a wide variety of embedded CPU families and target
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    BSPs.  Switching between RTEMS BSPs is accomplished via setting
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    the environment variable "RTEMS_MAKEFILE_PATH."
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    This description attempts to cover all aspects of the Makefile tree.  Most
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    of what is described here is maintained automatically by the configuration
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    files.
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    The example makefiles in make/Templates should be used as a starting
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    point for new directories.
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    There are 2 main types of Makefile:
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        directory and leaf.
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    Directory Makefiles
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    -------------------
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        A Makefile in a source directory with sub-directories is called a
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        "directory" Makefile.
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        Directory Makefile's are simply responsible for acting as "middle-men"
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        and recursing into their sub-directories and propagating the make.
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        For example, directory src/bin will contain only a Makefile and
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        sub-directories.  No actual source code will reside in the directory.
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        The following commands:
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            $ cd src/bin
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            $ make all
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        would descend into all the subdirectories of 'src/bin' and recursively
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        perform a 'make all'.
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        A 'make debug' will recurse thru sub-directories as a debug build.
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        A template directory Makefile which should work in almost all
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        cases is in make/Templates/Makefile.dir
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    Leaf Makefiles
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    --------------
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        Source directories that contain source code for libraries or
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        programs use a "leaf" Makefile.
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        These makefiles contain the rules necessary to build programs
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        (or libraries).
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        A template leaf Makefile is in Templates/Makefile.leaf .  A template
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        leaf Makefile for building libraries is in Templates/Makefile.lib .
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    NOTE: To simplify nested makefile's and source maintenance, we disallow
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    combining source and directories (that make(1) would be expected to
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    recurse into) in one source directory.  Ie., a directory in the source
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    tree may contain EITHER source files OR recursive sub directories, but NOT
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    both.  This assumption is generally shared with GNU automake.
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    Variants (where objects go)
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    ---------------------------
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        All binary targets are placed in a sub-directory whose name is (for
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        example):
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            o-optimize/       -- optimized binaries
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            o-debug/          -- debug binaries
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            o-profile/        -- profiling binaries
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        Using the template Makefiles, this will all happen automatically.
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        The contents of these directories are specific to a BSP.
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        Within a Makefile, the ${ARCH} variable is set to o-optimize,
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        o-debug, etc., as appropriate.
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        HISTORICAL NOTE: Prior to version 4.5, the name of the sub-directory
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          in which objects were placed included the BSP name.
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        Typing 'make' will place objects in o-optimize.
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        'make debug' will place objects in o-debug.
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        'make profile' will place objects in o-profile.
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        The debug and profile targets are equivalent to 'all' except that
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        CFLAGS and/or LDFLAGS are modified as per the compiler config file for
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        debug and profile support.
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        The targets debug, profile, etc., can be invoked recursively at
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        the directory make level.  So from the top of a tree, one could
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        install a debug version of everything under that point by:
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            $ cd src/lib
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            $ gmake debug
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            $ gmake install
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        When building a command that is linked with a generated library, the
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        appropriate version of the library will be linked in.
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        For example, the following fragments link the normal, debug, or
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        profile version of "libmine.a" as appropriate:
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            LD_LIBS   += $(LIBMINE)
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            LIBMINE = ../libmine/${ARCH}/libmine.a
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            ${ARCH}/pgm: $(LIBMINE) ${OBJS}
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                $(make-exe)
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        If we do 'gmake debug', then the library in
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        ../libmine/o-debug/libmine.a will be linked in.  If $(LIBMINE)
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        might not exist (or might be out of date) at this point, we could add
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            ${LIBMINE}: FORCEIT
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                cd ../libmine; ${MAKE} ${VARIANT_VA}
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        The above would generate the following command to build libmine.a:
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            cd ../libmine; gmake debug
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        The macro reference ${VARIANT_VA} converts ${ARCH} to the word 'debug'
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        (in this example) and thus ensures the proper version of the library
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        is built.
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    Targets
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    -------
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        All Makefile's support the following targets:
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            all                     -- make "everything"
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            install                 -- install "everything"
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        The following targets are provided automatically by
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        the included config files:
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            clean                   -- delete all targets
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            depend                  -- build a make dependency file
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            "variant targets"       -- special variants, see below
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        All directory Makefiles automatically propagate all these targets.  If
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        you don't wish to support 'all' or 'install' in your source directory,
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        you must leave the rules section empty, as the parent directory Makefile
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        will attempt it on recursive make's.
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    Configuration
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    -------------
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        All the real work described here happens in file(s) included
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        from your Makefile.
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        All Makefiles include a customization file which is used to select
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        compiler and host operating system.  The environment variable
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        RTEMS_MAKEFILE_PATH must point to the directory containing this file; eg:
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                export RTEMS_MAKEFILE_PATH=/.../pc386/
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        All leaf Makefile's also include either 'make/leaf.cfg' (or
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        'make/lib.cfg' for building libraries).  These config files provide
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        default rules and set up the command macros as appropriate.
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        All directory Makefiles include 'make/directory.cfg'.  directory.cfg
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        provides all the rules for recursing through sub directories.
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        The Makefile templates already perform these include's.
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        'make/leaf.cfg' (or directory.cfg) in turn includes:
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            a file specifying general purpose rules appropriate for
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                both leaf and directory makefiles.
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                ( make/main.cfg )
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            personality modules specified by the customization file for:
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                compiler            ( make/compilers/??.cfg )
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        generic rules file
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        ------------------
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            [ make/main.cfg ]
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            included by leaf.cfg or directory.cfg.
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            This file contains some standard rules and variable assignments
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            that all Makefiles need.
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            It also includes the FORCEIT: pseudo target.
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        OS config file for host machine
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        -------------------------------
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            [ make/os/OS-NAME.cfg ]
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            included by main.cfg
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            Figures out the target architecture and specifies command names
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            for the OS tools including RCS/CVS (but NOT for the compiler tools).
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        Compiler configuration for the target
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        -------------------------------------
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            [ compilers/COMPILER-NAME.cfg ]
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            included by leaf.cfg
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            Specifies the names of tools for compiling programs.
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            Names in here should be fully qualified, and NOT depend on $PATH.
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            Also specifies compiler flags to be used to generate optimized,
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            debugging and profile versions, as well as rules to compile
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            assembly language and make makefile dependencies.
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    Configuration Variables
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    -----------------------
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        Variables you have to set in the environment or in your Makefile.
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        Note: the RTEMS module files set RTEMS_ROOT and RTEMS_CUSTOM
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        for you.
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        Makefile Variables
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        ------------------
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            RTEMS_BSP        -- name of your 'bsp' eg: pc386, mvme136
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            RTEMS_CPU        -- CPU architecture e.g.: i386, m68k
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            RTEMS_CPU_FAMILY -- CPU model e.g.: i486dx, m68020
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            RTEMS_ROOT     -- The root of your source tree.
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                              All other file names are derived from this.
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                              [ eg: % setenv RTEMS_ROOT $HOME/work/RTEMS ]
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            RTEMS_CUSTOM   -- name of your config files in make/custom
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                              Example:
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                                 $(RTEMS_ROOT)/make/custom/$(RTEMS_BSP).cfg
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            The value RTEMS_ROOT is used in the custom
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            files to generate the make(1) variables:
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                PROJECT_RELEASE
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                PROJECT_BIN
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                PROJECT_INCLUDE
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                PROJECT_TOOLS
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            etc., which are used within the make config files themselves.
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            (The files in make/*.cfg try to avoid use of word RTEMS so
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            they can be more easily shared by other projects)
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        Preset variables
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        ----------------
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            Aside from command names set by the OS and compiler config files,
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            a number of MAKE variables are automatically set and maintained by
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            the config files.
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            PROJECT_RELEASE
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                        -- release/install directory
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                           [ $(PROJECT_ROOT) ]
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            PROJECT_BIN
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                        -- directory for installed binaries
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                           [ $(PROJECT_ROOT)/bin ]
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            PROJECT_TOOLS
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                        -- directory for build environment commands
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                           [ eg: $(PROJECT_ROOT)/build-tools ]
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            ARCH        -- target sub-directory for object code
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                           [ eg: o-optimize or o-debug ]
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            VARIANTS    -- full list of all possible values for $(ARCH);
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                           used mainly for 'make clean'
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                           [ eg: "o-optimize o-debug o-profile" ]
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            VARIANT_VA  -- Variant name.
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                           Normally "", but for 'make debug' it is "debug",
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                           for 'make profile', "profile, etc.
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                           see make/leaf.cfg for more info.
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        Preset compilation variables
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        ----------------------------
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          This is a list of some of the compilation variables.
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          Refer to the compiler config files for the complete list.
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            CFLAGS_OPTIMIZE_V   -- value of optimize flag for compiler
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                                   [ eg: -O ]
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            CFLAGS_DEBUG_V      -- value of debug flag for compiler
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                                   [ eg: -g ]
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            CFLAGS_PROFILE_V    -- compiler profile flags
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                                   [ eg: -pg ]
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            CFLAGS_DEBUG_OPTIMIZE_V
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                                -- optimize flag if compiling for debug
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                                     [ eg: "" ]
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            CFLAGS_DEBUG
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            CFLAGS_PROFILE
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            CFLAGS_OPTIMIZE     -- current values for each depending
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                                    on make variant.
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            LDFLAGS_STATIC_LIBRARIES_V
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                                -- ld option for static libraries
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                                    -Bstatic or -dy (svr4)
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            LDFLAGS_SHARED_LIBRARIES_V
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                                -- ld option for dynamic libraries
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                                    -Bdynamic or -dn (svr4)
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            Makefile Variables
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            ------------------
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                The following variables may be set in a typical Makefile.
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                C_PIECES    -- File names of your .c files without '.c' suffix.
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                               [ eg: C_PIECES=main funcs stuff ]
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                CC_PIECES   -- ditto, except for .cc files
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                S_PIECES    -- ditto, except for .S files.
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                LIB         -- target library name in leaf library makefiles.
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                               [ eg: LIB=${ARCH}/libmine.a ]
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                H_FILES     -- your .h files in this directory.
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                               [ eg: H_FILES=stuff.h extra.h ]
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                DEFINES     -- cc -D items.  Included in CPPFLAGS.
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                               leaf Makefiles.
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                               [ eg: DEFINES += -DUNIX ]
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                CPPFLAGS    -- -I include directories.
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                               leaf Makefiles.
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                               [ eg: CPPFLAGS += -I../include ]
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                LD_PATHS    -- arguments to -L for ld.
385
                               Will be prefixed with '-L' or '-L ' as appropriate
386
                               and included in LDFLAGS.
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                LDFLAGS     -- -L arguments to ld; more may be ADDed.
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                LD_LIBS     -- libraries to be linked in.
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                               [ eg: LDLIBS += ../libfoo/${ARCH}/libfoo.a ]
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                XCFLAGS     -- "extra" CFLAGS for special needs.  Pre-pended
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                               to CFLAGS.
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                               Not set or used by Makefiles.
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                               Can be set on command line to pass extra flags
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                               to the compiler.
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                XCPPFLAGS   -- ditto for CPPFLAGS
400
                               Can be set on command line to pass extra flags
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                               to the preprocessor.
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                XCCPPFLAGS  -- same as XCPPFLAGS for C++.
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405
                XCCFLAGS    -- same as XCFLAGS for C++.
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                SUBDIRS    -- list of sub directories for make recursion.
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                               directory Makefiles only.
409
                               [ eg: SUBDIRS=cpu bsp ]
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411
                CLEAN_ADDITIONS
412
                            -- list of files or directories that should
413
                               be deleted by 'make clean'
414
                               [ eg: CLEAN_ADDITIONS += y.tab.c ]
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416
                               See 'leaf.cfg' for the 'clean:' rule and its
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                               default deletions.
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                CLOBBER_ADDITIONS
420
                            -- list of files or directories that should
421
                               be deleted by 'make clobber'
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                               Since 'make clobber' includes 'make clean',
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                               you don't need to duplicate items in both.
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425
            Command names
426
            -------------
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428
                The following commands should only be called
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                as make variables:
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431
                    MAKE,INSTALL,INSTALL_VARIANT,SHELL
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                    ECHO,CAT,CP,MV,LN,MKDIR,CHMOD
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                    SED
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                    CC,CPP,AS,AR,LD,NM,SIZE,RANLIB,MKLIB,
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                    YACC,LEX,LINT,CTAGS,ETAGS
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                 In addition, the following commands specifically support
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                 the installation of libraries, executables, header files,
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                 and other things that need to be installed:
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                    INSTALL_CHANGE  - install a file only if the source
445
                                      file is actually different than
446
                                      the installed copy or if there is
447
                                      no installed copy.  USAGE:
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449
      usage: install-if-change [ -vmV ] file [ file ... ] dest-directory-or-file
450
        -v          -- verbose
451
        -V suffix   -- suffix to append to targets (before any . suffix)
452
                        eg: -V _g would change 'foo' to 'foo_g' and
453
                                               'libfoo.a' to 'libfoo_g.a'
454
        -m mode     -- mode for new file(s)
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                    INSTALL_VARIANT - installs the built file using the
457
                                      proper variant suffix (e.g. _g
458
                                      for debug turns libmine.a into libmine_g.a)
459
                                      This is implemented as a macro that
460
                                      invokes install-if-change with the
461
                                      appropriate -V argument setting.
462
 
463
            Special Directory Makefile Targets
464
            ----------------------------------
465
 
466
                all_WRAPUP
467
                clean_WRAPUP
468
                install_WRAPUP
469
                clean_WRAPUP
470
                clobber_WRAPUP
471
                depend_WRAPUP
472
                            -- Specify additional commands for recursive
473
                               (directory level) targets.
474
 
475
                               This is handy in certain cases where you need
476
                               to do bit of work *after* a recursive make.
477
 
478
    make/Templates
479
    --------------
480
 
481
        This directory contains Makefile and source file templates that
482
        should help in creating or converting makefiles.
483
 
484
        Makefile.leaf
485
            Template leaf Makefiles.
486
 
487
        Makefile.lib
488
            Template leaf library Makefiles.
489
 
490
        Makefile.dir
491
            Template "directory" makefile.
492
 
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