-# Copyright (C) 2012 W. Trevor King
+# Copyright (C) 2012-2013 W. Trevor King
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
PACKAGE = hw0
VERSION = 1
RELEASE = $(COURSE)-$(PACKAGE)-$(VERSION)
-PROGRAM = hello_world
+RUN_PROGRAM = hello_world
+SCRIPTS =
+C_PROGRAMS = hello_world
+CXX_PROGRAMS = goodbye_world
+PROGRAMS = $(C_PROGRAMS) $(CXX_PROGRAMS)
# Define the source files that will be distributed in the tarball
-SOURCE = *.c COPYING Makefile README
+SOURCE = *.c *.cpp *.h COPYING Makefile README $(SCRIPTS)
-# Define a list of object files needed to link PROGRAM
-OBJECTS = $(PROGRAM).o
+# Define a list of object files needed to link PROGRAM. We're setting
+# things up here so that a program % depends on the object file %.o.
+# For details on `foreach` and `eval`, see
+# http://www.gnu.org/software/make/manual/html_node/Foreach-Function.html
+# http://www.gnu.org/software/make/manual/html_node/Eval-Function.html
+$(foreach PROGRAM, $(PROGRAMS), $(eval $(PROGRAM)_OBJECTS = $(PROGRAM).o))
+
+# You can override a paricular case here with something like:
+#hello_world_OBJECTS = hello_world.o utility_code.o
# You may want to link agains external libraries. For example, to
# link against the system math library, use.
-# LIBS = -lm
-LIBS =
+# hello_world_LIBS = -lm
+$(foreach PROGRAM, $(PROGRAMS), $(eval $(PROGRAM)_LIBS =))
# Define useful programs (this makes it easy to swap in alternates)
CP = cp
# Declare targets that do not generate files of the same name.
# http://www.gnu.org/software/make/manual/html_node/Phony-Targets.html
-.PHONY: all help clean dist run
+.PHONY: all help clean dist run print- printvars
# target: all - the default target
-all: $(PROGRAM)
+# The target of the first rule is the default goal. See:
+# http://www.gnu.org/software/make/manual/html_node/Rules.html
+all: $(PROGRAMS)
# target: help - display callable targets
# Use `grep` to search this file for target comments
# target: clean - remove automatically generated files
clean:
- $(RM) -rf $(PROGRAM) *.o $(RELEASE)*
+ $(RM) -rf $(PROGRAMS) *.o $(RELEASE)*
# target: dist - generate a tarball packaging the source
# Here, we move the source into a temporary release directory, tar the
# target: hello_world - compile the hello_world program
# Use GCC to link the program from object files.
-$(PROGRAM): $(OBJECTS)
- $(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
+# For an explanation of the static pattern rule syntax:
+# targets ...: target-pattern: prereq-patterns ...
+# see
+# http://www.gnu.org/software/make/manual/html_node/Static-Usage.html
+# For an explanation of $@, $^, and other special variables, see
+# http://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html
+# For an explanation of .SECONDEXPANSION, see
+# http://www.gnu.org/software/make/manual/html_node/Secondary-Expansion.html
+# `$$` escapes make-variable expansion for the first pass through the
+# recipe. See
+# http://www.gnu.org/software/make/manual/html_node/Variables-in-Recipes.html
+#
+# What's going on here? During the read-in phase, Make expands the
+# rule to
+# hello_world goodbye_world: % : $($(@)_OBJECTS)
+# Because we're using .SECONDEXPANSION, Make expands the prerequisites
+# again during the target-update phase. If we're building
+# hello_world, $(@) will expand to hello_world, and we'll have
+# hello_world goodbye_world: hello_world : $(hello_world_OBJECTS)
+# as the variable expansion continues, we end up with
+# hello_world goodbye_world: hello_world : hello_world.o
+# which is the final rule used to determine the prerequisites.
+#
+# The recipe expands to
+# cc -o hello_world hello_world.o $(hello_world_LIBS)
+# which expands to (if hello_world_LIBS was set to `-lm`)
+# cc -o hello_world hello_world.o -lm
+#
+# Striking the right balance between "everything handled
+# automatically" (i.e. "complicated") and "everything handled
+# manually" (i.e. tedious) is difficult, and maybe this rule crosses
+# the line. The simpler alternative would be to define your own
+# prerequisites for each program you wish to compile, and you're
+# certainly allowed to go that route if you wish.
+.SECONDEXPANSION:
+$(C_PROGRAMS): % : $$($$(@)_OBJECTS)
+ $(CC) $(LDFLAGS) -o "$@" $^ $($(@)_LIBS)
+
+.SECONDEXPANSION:
+$(CXX_PROGRAMS): % : $$($$(*)_OBJECTS)
+ $(CXX) $(LDFLAGS) -o "$@" $^ $($(@)_LIBS)
# target: run - use the program for its intended purpose
-# Here we just execute PROGRAM, but you could also use something like
-# run: $(PROGRAM) plot.gp
-# ./$(PROGRAM) > data
+# Here we just execute RUN_PROGRAM, but you could also use something
+# like
+# run: $(RUN_PROGRAM) plot.gp
+# ./$(RUN_PROGRAM) > data
# gnuplot plot.gp
# where plot.gp was a gnuplot script for plotting data generated by
-# PROGRAM.
-run: $(PROGRAM)
- ./$(PROGRAM)
+# RUN_PROGRAM.
+run: $(PROGRAMS)
+ ./$(RUN_PROGRAM)
-# Matching rule for compiling object files from C++ source
+# Pattern rule for compiling object files from C++ source
# There is an implicit rule for this in GNU make
# http://www.gnu.org/software/make/manual/html_node/Catalogue-of-Rules.html
-# but I redefine it here for clarity.
+# but I redefine it here for clarity. For an explanation of the
+# %.o: %.cpp
+# syntax, see
+# http://www.gnu.org/software/make/manual/html_node/Pattern-Intro.html
#
# CXX and CXXFLAGS have defaults defined by make
# http://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
# for example, try
# $ make CXX=/usr/local/bin/g++ CXXFLAGS=-Wall
%.o: %.cpp
- $(CXX) $(CXXFLAGS) -c $<
+ $(CXX) $(CXXFLAGS) -c "$<"
-# Matching rule for compiling object files from C source
+# Pattern rule for compiling object files from C source
# The comments from the C++ rule above also apply here
%.o: %.c
- $(CC) $(CFLAGS) -c $<
+ $(CC) $(CFLAGS) -c "$<"
+
+# target: print-% - display a variable value (e.g. print-PROGRAMS)
+# Take some of the mystery out of variable manipulation. For example,
+# $ make print-hello_world_OBJECTS
+# The `@` suppresses recipe echoing. See
+# http://www.gnu.org/software/make/manual/html_node/Echoing.html
+# The `info` function acts like the shell `echo` command. See
+# http://www.gnu.org/software/make/manual/html_node/Make-Control-Functions.html
+# For an explanation of $* and other special variables, see
+# http://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html
+print-%:
+ @$(info $* = $($*))
+
+# target: printvars - display all non-default variables
+# .VARIBALES holds a list of all global variables. See
+# http://www.gnu.org/software/make/manual/html_node/Special-Variables.html
+# The functions---`sort`, `if`, `filter-out`, `origin`, `warning`, and
+# `value`--- are discussed, respectively, here:
+# http://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-sort-580
+# http://www.gnu.org/software/make/manual/html_node/Conditional-Functions.html
+# http://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-filter_002dout-577
+# http://www.gnu.org/software/make/manual/html_node/Origin-Function.html
+# http://www.gnu.org/software/make/manual/html_node/Value-Function.html
+printvars:
+ @$(foreach V, \
+ $(sort $(.VARIABLES)), \
+ $(if \
+ $(filter-out environment default automatic, \
+ $(origin $V)), \
+ $(info $V=$($V) (origin: $(origin $V), value: $(value $V))) \
+ ) \
+ )
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