# Comfignat makefile foundation for configuring and building GNAT projects
# Copyright 2013 B. Persson, Bjorn@Rombobeorn.se
#
# This material is provided as is, with absolutely no warranty expressed
# or implied. Any use is at your own risk.
#
# Permission is hereby granted to use or copy this makefile
# for any purpose, provided the above notices are retained on all copies.
# Permission to modify the code and to distribute modified code is granted,
# provided the above notices are retained, and a notice that the code was
# modified is included with the above copyright notice.


# This file contains generic Make code. It is designed to be included by other
# makefiles, called containing makefiles, which add information specific to the
# project at hand. Builds are controlled by GNAT project files which import the
# abstract project Comfignat and use the directory variables it defines. For
# libraries there shall also be usage projects to be installed on the target
# system. Usage projects and the Comfignat project will be preprocessed with
# Gnatprep. (Build projects may also be preprocessed.)
#
# If a directories project is provided, then the project files will get the
# directory variables from there, otherwise the Make variables will be used.
#
# This file may not work with other Make clones than GNU Make. (Reusable Make
# code is pretty much impossible to write without advanced Make features.) If
# Make cannot be used for whatever reason, then it's not too difficult to run
# the project files through Gnatprep manually.


#
# Program-name variables and the usual options variables are picked up from the
# environment or the command line:
#

GNATPREP     ?= gnatprep
GNAT_BUILDER ?= gprbuild

# If GNAT_BUILDER looks like it will invoke Gnatmake, then make the default
# value of GNATFLAGS compatible with Gnatmake. Otherwise make it suitable for
# building multi-language projects with GPRbuild.
GNATFLAGS ?= ${if ${findstring gnatmake, \
                               ${notdir ${call mung,${GNAT_BUILDER}}}}, \
                  ${GNAT_BUILDER_FLAGS} \
                     -cargs ${ADAFLAGS} \
                     -bargs ${GNATBINDFLAGS} \
                     -largs ${GNATLINKFLAGS} ${LDFLAGS}, \
                  ${GNAT_BUILDER_FLAGS} \
                     -cargs:Ada ${ADAFLAGS} \
                     -cargs:C ${CPPFLAGS} ${CFLAGS} \
                     -cargs:C++ ${CPPFLAGS} ${CXXFLAGS} \
                     -cargs:Fortran ${FFLAGS} \
                     -bargs ${GNATBINDFLAGS} \
                     -largs ${LDFLAGS}}

# (DESTDIR is also supported.)

# Containing makefiles may assign default values to the options variables
# GNAT_BUILDER_FLAGS, ADAFLAGS, CPPFLAGS, CFLAGS, CXXFLAGS, FFLAGS,
# GNATBINDFLAGS, GNATLINKFLAGS and LDFLAGS if they are undefined in the
# environment, but should expect that users and distributions may override
# those defaults.


#
# These variables should be overridden on the command line as needed, but will
# not be picked up from the environment:
#

dirgpr =
# dirgpr should be the filename of the target system's directories project if
# there is one. The Gnatprep symbols Directories_GPR and Directories_Project
# will be derived from dirgpr, and project files will be configured to use the
# directories project.

relocatable_package = false
# If relocatable_package is true, then directory variables in project files
# will be configured with relative pathnames so that the installed directory
# tree as a whole can be moved to another location in the filesystem without
# breaking the project files.
# dirgpr takes precedence over relocatable_package.

prefix        = /usr/local
exec_prefix   = ${prefix}
bindir        = ${exec_prefix}/bin
libexecdir    = ${exec_prefix}/libexec
datarootdir   = ${prefix}/share
datadir       = ${datarootdir}
sysconfdir    = ${prefix}/etc
localstatedir = ${prefix}/var
statedir      = ${localstatedir}/lib
cachedir      = ${localstatedir}/cache
logdir        = ${localstatedir}/log
runtimedir    = /run
lockdir       = ${runtimedir}/lock
includedir    = ${prefix}/include
libdir        = ${exec_prefix}/lib
gprdir        = ${datarootdir}/gpr
localedir     = ${datarootdir}/locale
mandir        = ${datarootdir}/man
infodir       = ${datarootdir}/info
miscdocdir    = ${datarootdir}/doc
# These are the directories where different kinds of files will be installed on
# the target system. Some of these directory variables aren't used in this file
# but may be needed in containing makefiles.

builddir = ${CURDIR}/build
objdir   = ${builddir}/obj
stagedir = ${builddir}/stage
# Intermediate files produced during the build are kept in objdir. Files to be
# installed are written to stagedir, and then copied to their destination in
# the installation step.

# Containing makefiles should avoid modifying the directory variables. Users
# should be able to rely on these defaults.

install_cp_flags = ${if ${DESTDIR},--preserve=timestamps,}
# Timestamps are preserved when installation is done to a staging directory. 
# This matters for files that aren't generated during the build but copied from
# the source tree. Timestamps are not preserved when installation is done
# directly to the target system, because that would change the timestamps of 
# existing directories.


#
# Containing makefiles should assign or append to these variables as needed:
#

ifneq (${origin preprocessed_files},file)
   preprocessed_files := ${basename ${wildcard *.in}}
endif
# preprocessed_files is a list of files to be produced in the preprocessing
# step at the beginning of the build. Containing makefiles may override it or
# append additional filenames to it.

ifneq (${origin build_GPRs},file)
   build_GPRs :=
endif
# build_GPRs shall name one or more project files for building the software.
# These project files will be used when "make" or "make build" is invoked.

ifneq (${origin usage_GPRs},file)
   usage_GPRs :=
endif
# If the build produces libraries, then usage_GPRs shall name the project files
# that other projects should import to link to the libraries. These project
# files will be installed to the target system.

ifneq (${origin options},file)
   options :=
endif
# options may be assigned a list of variable names. Those variables may be
# overridden on the command line, and will be defined as Gnatprep symbols.
# Their values must be "true" or "false".
# The containing makefile should assign a default value to each variable unless
# it shall be mandatory to always set the option on the command line.

ifneq (${origin Gnatprep_definitions},file)
   Gnatprep_definitions :=
endif
# Any text assigned to Gnatprep_definitions will be included in the Gnatprep
# command line. It may be used for additional symbol definitions.

configuration_variables += \
   GNATPREP GNAT_BUILDER \
   GNAT_BUILDER_FLAGS ADAFLAGS CPPFLAGS CFLAGS CXXFLAGS FFLAGS GNATBINDFLAGS \
   GNATLINKFLAGS LDFLAGS GNATFLAGS \
   DESTDIR \
   dirgpr relocatable_package \
   prefix exec_prefix bindir libexecdir datarootdir datadir sysconfdir \
   localstatedir statedir cachedir logdir runtimedir lockdir includedir libdir \
   gprdir localedir mandir infodir miscdocdir \
   builddir objdir stagedir \
   install_cp_flags \
   ${options}
# configuration_variables is a list of variables that can be saved in the
# persistent configuration with "make configure". Containing makefiles may
# append additional variable names.


#
# Containing makefiles may use this command variable:
#

build_GPR = "${GNAT_BUILDER}" -P ${firstword ${filter %.gpr,$^}} -p \
            ${GNATFLAGS} -margs
# build_GPR is a command for use in recipes. It performs a build controlled by
# the first project file among the rule's prerequisites.
# Containing makefiles may append additional arguments for the builder, but
# should ensure that any arguments that aren't essential for the build to work
# can be overridden from the command line. Global default values for optional
# arguments should be set in the options variables instead.


#
# Read the configuration file if there is one:
#

-include comfignat_configuration.mk


#
# Compute the symbol definitions for Gnatprep, and some other data that the
# rules need:
#

nil =
space_sub = _Comfignat_magic_protective_space_character_substitute_
percent_sub = _Comfignat_magic_protective_percent_character_substitute_
mung = ${subst %,${percent_sub},${subst ${nil} ,${space_sub},${1}}}
unmung = ${subst ${percent_sub},%,${subst ${space_sub}, ,${1}}}
# mung and unmung are used to prevent Make from interpreting space and percent
# characters in strings.

# Convey objdir and stagedir to Gnatprep.
directories := '-DObjdir="${objdir}"' '-DStagedir="${stagedir}"'
# directories is simply expanded as this reduces redundant processing and the
# directory variables are not to be modified after this point.

ifneq (${dirgpr},)

   # A directories project is used, so make project files take the directory
   # variables from there.

   directories_project := ${basename ${notdir ${dirgpr}}}
   directories += '-DDirectories_GPR="${dirgpr}"'
   directories += '-DDirectories_Project=${directories_project}'
   directories += '-DPrefix="${prefix}"'
   directories += '-DExec_Prefix="${exec_prefix}"'
   directories += '-DBindir=${directories_project}.Bindir'
   directories += '-DLibexecdir=${directories_project}.Libexecdir'
   directories += '-DIncludedir=${directories_project}.Includedir'
   directories += '-DLibdir=${directories_project}.Libdir'

else ifeq (${relocatable_package},true)

   # Make project files use directory names relative to gprdir.

   relativize = ${if ${filter ${2}%,${1}}, \
                     ${3}${1:${2}%=%}, \
                     ${call relativize,${1},${dir ${2:%/=%}},${3}../}}
   # relativize is the recursive algorithm that converts an absolute pathname
   # into a relative one.
   # Parameters:
   #    1: an absolute pathname to convert to relative
   #    2: the absolute base pathname, being shortened until it's a prefix of 1
   #    3: a growing series of "../" to lead the relative pathname with
   # If 2 is a prefix of 1, then return 3 concatenated with the part of 1 that
   # differs from 2. Otherwise delete the last element of 2, add one level of
   # "../" to 3, and repeat.
   # Within relativize all pathnames have one trailing slash so that only whole
   # directory names will match. Otherwise "/usr/lib" could match "/usr/lib64"
   # for example.

   prep = ${subst //,/,${abspath ${call mung,${1}}}/}
   # prep prepares a pathname for use as a parameter to relativize.
   #    · Protect space and percent characters from interpretation by Make.
   #    · Normalize the pathname, eliminating ".", ".." and "//".
   #    · Append a slash.
   #    · If the input was "/", then it is now "//". Change that back to "/".

   relative_to_gprdir = \
      ${or ${call unmung,${patsubst %/,%,${call relativize \
                                               ,${call prep,${1}} \
                                               ,${call prep,${gprdir}},}}},.}
   # relative_to_gprdir converts an absolute pathname into a pathname relative
   # to gprdir. What it actually does is to prepare the input to relativize and
   # fix up its output.
   #    · Prepare the input pathname with prep.
   #    · Prepare gprdir with prep.
   #    · Call relativize with the input for parameter 1, gprdir for 2, and an
   #      empty string for 3.
   #    · Strip the result of surrounding spaces and the trailing slash.
   #    · Reverse the protection of space and percent characters.
   #    · If the result is an empty string, then return "." instead.

   directories += '-DBase="${gprdir}"'
   directories += '-DPrefix="${call relative_to_gprdir,${prefix}}"'
   directories += '-DExec_Prefix="${call relative_to_gprdir,${exec_prefix}}"'
   directories += '-DBindir="${call relative_to_gprdir,${bindir}}"'
   directories += '-DLibexecdir="${call relative_to_gprdir,${libexecdir}}"'
   directories += '-DIncludedir="${call relative_to_gprdir,${includedir}}"'
   directories += '-DLibdir="${call relative_to_gprdir,${libdir}}"'

else ifeq (${relocatable_package},false)

   # Convey the directory variables unmodified to project files.

   directories += '-DPrefix="${prefix}"'
   directories += '-DExec_Prefix="${exec_prefix}"'
   directories += '-DBindir="${bindir}"'
   directories += '-DLibexecdir="${libexecdir}"'
   directories += '-DIncludedir="${includedir}"'
   directories += '-DLibdir="${libdir}"'

else
   ${error relocatable_package must be "true" or "false".}
endif

definitions = ${directories}
# definitions is recursively expanded so that the options referenced below may
# be defined in containing makefiles after the inclusion of this file.

# Convey boolean options to Gnatprep.
definitions += \
   ${foreach option,${options}, \
             ${if ${and ${filter-out environment,${origin ${option}}}, \
                        ${filter 1,${words ${${option}}}}, \
                        ${filter true false,${${option}}}}, \
                  -D${option}=${${option}}, \
                  ${error ${option} must be "true" or "false".}}}
# For each variable listed in options, check that it didn't come from the
# environment (to prevent accidents), that its value is a single word, and that
# that word is either "true" or "false". If so, append a symbol definition;
# otherwise complain and stop.

# Convey any additional symbols that the containing makefile has defined.
definitions += ${Gnatprep_definitions}

build_targets = ${addsuffix .phony_target,${build_GPRs}}
# A phony target is defined for each build project, and the job of determining
# whether the project needs rebuilding is delegated to the builder.

stage_any_GPRs = ${if ${usage_GPRs},stage_GPRs}
# The recipe for the target stage_GPRs breaks if usage_GPRs is empty, so it's
# included as a prerequisite of build only if there are some usage projects.


#
# Make rules:
#

.SECONDEXPANSION:

all: build

configure::
	@( ${foreach variable,${configuration_variables}, \
	             ${if ${or ${findstring command line, \
	                                    ${origin ${variable}}}, \
	                       ${filter true,${${variable}_is_configured}}}, \
	                  echo '${variable} = ${value ${variable}}'; \
	                  echo '${variable}_is_configured = true';}} \
	 ) > comfignat_configuration.mk
# Out of the variables listed in configuration_variables, all that were
# overridden on the command line, and all that were previously configured, are
# written to the configuration file. A variable is considered previously
# configured if there is another variable with "_is_configured" appended to its
# name and a value of "true". Such a variable is also written for each
# configured variable. It is therefore possible to delete a variable V from the
# configuration by running "make configure V_is_configured=false".

%.gpr: %.gpr.in
	"${GNATPREP}" $< $@ ${definitions}

preprocess: $${preprocessed_files}

%.gpr.phony_target: %.gpr preprocess
	${build_GPR}
# Instead of tracking dependencies between project files, this rule simply
# requires that all preprocessing is done before any project is built.

stage_GPRs: $${usage_GPRs}
	mkdir -p "${stagedir}${gprdir}"
	cp -p ${usage_GPRs} "${stagedir}${gprdir}"
.PHONY: stage_GPRs

build: $${build_targets} $${stage_any_GPRs}

${stagedir}:
	@${MAKE} build --no-print-directory
# "make install" straight out of a source package triggers a build, but if
# something has been built then "make install" doesn't rebuild anything, just
# copies the built files to their destination.

install: ${stagedir}
	mkdir -p "${DESTDIR}/"
	cp -RPf ${install_cp_flags} "${stagedir}"/* "${DESTDIR}/"
.PHONY: install

clean::
	rm -Rf ${builddir} ${preprocessed_files}

unconfigure::
	rm -f comfignat_configuration.mk

distclean: clean unconfigure