Makefile

################################################################################
# Generic Makefile, tested with gcc and Linux and clang and OSX.
#
# For make documentation see:
# https://www.gnu.org/software/make/manual/make.html
#

# default target
all:

# build: debug by default, eg: 'make build=release'
build := debug

# architecture: eg: x86-64, core2, corei7, core-avx-i or native
arch := x86-64

################################################################################
# Locations

# Local build or an installation
ifdef CONDA_PREFIX
ENV := $(CONDA_PREFIX)
else
ENV := $(PREFIX)
endif

inc_sysroot := ${CONDA_BUILD_SYSROOT}
inc_conda := ${ENV}/include
inc_python := $(shell python -c "from distutils.sysconfig import get_python_inc; print(get_python_inc())")

src_dir := ${CURDIR}/src
inc_dir := ${CURDIR}/include
build_dir := ${CURDIR}/build/$(firstword $(shell uname -s))-$(firstword $(shell uname -r))-${arch}-${build}
bin_dir := ${build_dir}/bin
test_dir := ${build_dir}/test
lib_dir := ${build_dir}/lib
obj_dir := ${build_dir}/obj

################################################################################
# Common flags and libraries (lowercase, target specific are uppercase)

cppflags := -march=${arch} -fpic -std=c++17 -Wall -isysroot ${inc_sysroot} -I${inc_dir} -isystem ${inc_conda} -isystem ${inc_python}
cppflags.debug := -g3
cppflags.release := -DNDEBUG -flto -O3

# Enable relative run-time linking to avoid setting LD_LIBRARY_PATH (works locally and in conda)
ldflags := -march=${arch} -fpic -Wall -isysroot ${CONDA_BUILD_SYSROOT} '-Wl,-rpath,$$ORIGIN/../lib' -L${lib_dir} -L${ENV}/lib
ldflags.debug :=
ldflags.release := -flto=auto -O3 -fuse-linker-plugin
syslibs := dl rt

# Enable link time optimization in static libraries using the gcc wrapper of AR
AR := ${GCC_AR}

################################################################################
# Targets

define BUILD_TARGET  # takes 2 arguments, target name and paths to object files
  ${1}: ${2}                          # target depends creating these objects
  ${2} :| $(dir ${2})                 # objects depend on their directories existing
  objs += ${2}
  obj_sub_dirs += $(dir ${2})
  ${1}: CPPFLAGS=                     # reset target specific cpp flags
  ${1}: LDFLAGS=                      # reset target specific linker flags
  ${1}: LIBS=                         # reset static and dynamic library linking
  ${1}: $(lastword $(MAKEFILE_LIST))  # relink if makefile has changed
endef

define STATIC_LIBRARY  # takes 2 arguments, library name and paths to cpp files
  static_libs += ${lib_dir}/$(addprefix lib,$(addsuffix .a,${1}))
  $(call BUILD_TARGET,${lib_dir}/$(addprefix lib,$(addsuffix .a,${1})),$(addprefix ${obj_dir}/, $(addsuffix .o,$(basename ${2})))))
endef

define SHARED_LIBRARY  # takes 2 arguments, library name and paths to cpp files
  shared_libs += ${lib_dir}/$(addprefix lib,$(addsuffix .so,${1}))
  $(call BUILD_TARGET,${lib_dir}/$(addprefix lib,$(addsuffix .so,${1})),$(addprefix ${obj_dir}/, $(addsuffix .o,$(basename ${2})))))
endef

define EXECUTABLE  # takes 2 arguments, executable name and paths to cpp files
  bins += ${bin_dir}/${1}
  $(call BUILD_TARGET,${bin_dir}/${1},$(addprefix ${obj_dir}/, $(addsuffix .o,$(basename ${2})))))
endef

define RUN_TEST  # takes 1 argument, test harness name
run_${1} : ${test_dir}/${1}
	@echo "--- Running test-harness ${1} ---"
	cd ${test_dir} && ${test_dir}/${1}
  run_tests += run_${1}
endef

define TEST_HARNESS  # build and run, takes 2 arguments, target name and paths to cpp files
  tests += ${test_dir}/${1}
  $(call BUILD_TARGET,${test_dir}/${1},$(addprefix ${obj_dir}/, $(addsuffix .o,$(basename ${2})))))
  $(call RUN_TEST,${1})
endef

################################################################################
# Project Targets

include build.mk

test: ${static_libs} ${shared_libs} ${tests} ${run_tests}
all: ${static_libs} ${shared_libs} ${bins} sym_links
clean:
	rm -rf ${build_dir}
	rm -f ${CURDIR}/lib
	rm -f ${CURDIR}/bin

.PHONY: all test clean

################################################################################
# Directory dependencies (to create directories)

# first remove duplicates
static_libs := $(sort ${static_libs})
shared_libs := $(sort ${shared_libs})
bins := $(sort ${bins})
tests := $(sort ${tests})
obj_sub_dirs := $(sort ${obj_sub_dirs})

${static_libs} :| ${lib_dir}
${shared_libs} :| ${lib_dir}
${bins} :| ${bin_dir}
${tests} :| ${test_dir}
${obj_sub_dirs} ${lib_dir} ${bin_dir} ${test_dir} :
	mkdir -p $@

################################################################################
# Rules and dependencies

define CXX_COMPILE
${CXX} -c -MMD -MP -o $@ ${CPPFLAGS} ${cppflags.${build}} ${cppflags} $<
endef

define CXX_EXECUTABLE
${CXX} -o $@ ${LDFLAGS} ${ldflags.${build}} ${ldflags} $(filter %.o,$^) $(addprefix -l,${LIBS}) $(addprefix -l,${syslibs})
endef

# Objects files depend on autogenerated dependencies files
-include $(objs:%.o=%.d)

# How to create object files from cpp files
${obj_dir}/%.o: ${src_dir}/%.cpp
	$(CXX_COMPILE)

# How to link static libraries
${static_libs}: ${lib_dir}/%.a:
	rm -f $@ && ${AR} crv $@ $(filter %.o,$^)

# How to link shared libraries
${shared_libs}: ${lib_dir}/%.so:
	${CXX} -shared -o $@ ${LDFLAGS} ${ldflags.${build}} ${ldflags} $(filter %.o,$^) $(addprefix -l,${LIBS})

# How to link executables
${bins}: ${bin_dir}/%:
	$(CXX_EXECUTABLE)

# How to link test harnesses
${tests}: ${test_dir}/%:
	$(CXX_EXECUTABLE)

# Update the current sym links to point to this build configuration
sym_links:
	ln -sf ${build_dir}/lib ${CURDIR}/.
	ln -sf ${build_dir}/bin ${CURDIR}/.