From: W. Trevor King Date: Fri, 5 Oct 2012 17:31:49 +0000 (-0700) Subject: Restore C++ example, and expad Makefile to handle multiple programs. X-Git-Url: http://git.tremily.us/?p=assignment-template.git;a=commitdiff_plain;h=ad70e0e54641f5507d5219c7ca28fdb56b506ca1 Restore C++ example, and expad Makefile to handle multiple programs. --- diff --git a/.gitignore b/.gitignore index 1c52c8a..3723be1 100644 --- a/.gitignore +++ b/.gitignore @@ -1,2 +1,3 @@ hello_world +goodbye_world *.o diff --git a/Makefile b/Makefile index 1e31bc7..5ff17ab 100644 --- a/Makefile +++ b/Makefile @@ -24,18 +24,28 @@ COURSE = phys405 PACKAGE = hw0 VERSION = 1 RELEASE = $(COURSE)-$(PACKAGE)-$(VERSION) -PROGRAM = hello_world +RUN_PROGRAM = hello_world +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 -# 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 @@ -49,7 +59,7 @@ TAR = tar .PHONY: all help clean dist run print- printvars # target: all - the default target -all: $(PROGRAM) +all: $(PROGRAMS) # target: help - display callable targets # Use `grep` to search this file for target comments @@ -58,7 +68,7 @@ help: # target: clean - remove automatically generated files clean: - $(RM) -rf $(PROGRAM) *.o $(RELEASE)* + $(RM) -rf $(PROGRAMS) *.o $(RELEASE)* # target: dist - generate a tarball packaging the source # Here, we move the source into a temporary release directory, tar the @@ -71,18 +81,58 @@ dist: # target: hello_world - compile the hello_world program # Use GCC to link the program from object files. -$(PROGRAM): $(OBJECTS) - $(CC) $(LDFLAGS) -o $@ $^ $(LIBS) +# For an explanation of the +# targets ...: target-pattern: prereq-patterns ... +# syntax, 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 +# `$$` escapes make-variable expansion for the first pass through the +# recipe. See +# http://www.gnu.org/software/make/manual/html_node/Variables-in-Recipes.html +# +# What's going on here? During the read-in phase, Make expands the +# rule to +# hello_world goodbye_world: % : $($(@)_OBJECTS) +# Because we're using .SECONDEXPANSION, Make expands the prerequisites +# again during the target-update phase. If we're building +# hello_world, $(@) will expand to hello_world, and we'll have +# hello_world goodbye_world: hello_world : $(hello_world_OBJECTS) +# as the variable expansion continues, we end up with +# hello_world goodbye_world: hello_world : hello_world.o +# which is the final rule used to determine the prerequisites. +# +# The recipe expands to +# gcc -o hello_world hello_world.o $(hello_world_LIBS) +# which expands to (if hello_world_LIBS was set to `-lm`) +# gcc -o hello_world hello_world.o -lm +# +# Striking the right balance between "everything handled +# automatically" (i.e. "complicated") and "everything handled +# manually" (i.e. tedious) is difficult, and maybe this rule crosses +# the line. The simpler alternative would be to define your own +# prerequisites for each program you wish to compile, and you're +# certainly allowed to go that route if you wish. +.SECONDEXPANSION: +$(C_PROGRAMS): % : $$($$(@)_OBJECTS) + $(CC) $(LDFLAGS) -o $@ $^ $($(@)_LIBS) + +.SECONDEXPANSION: +$(CXX_PROGRAMS): % : $$($$(*)_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 # There is an implicit rule for this in GNU make diff --git a/goodbye_world.cpp b/goodbye_world.cpp new file mode 100644 index 0000000..f9ec77f --- /dev/null +++ b/goodbye_world.cpp @@ -0,0 +1,27 @@ +/* +A simple "hello world" example in C++. + +Copyright (C) 2012 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 +the Free Software Foundation, either version 3 of the License, or +(at your option) any later version. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with this program. If not, see . +*/ + +#include + +using namespace std; + +int main() { + cout << "goodbye, world\n"; + return 0; +}