Paint: paint a graph with Makefile

Here I introduce a way of writing Makefile.

Features:

single logical Makefile using only absolute path in rules

When a Makefile include other Makefiles, essentially it's still a single logical Makefile, containing a single dependency graph.

If we call make in a recipt in a Makefile, there are at least two dependency graphs, or at least two logical Makefile.

The way in which we write Makefile:

• Never call make in recipts, only include other Makefiles.
• Only use absolute path in rules.

Then what you have is a single, simple, complete and straightforward dependency graph.

execute make anywhere

Most likely, the source code of your project has a tree structure and contains many directories.

The way in which we write Makefile:

• allow you to execute make in any directory

General Idea

1st, find out the absolute path of your project root directory.

Here is the code to figure out the absolute path of your project root directory:

ifndef PROJECT_ROOT
    sp :=
    sp +=
    anchor := prod/makefiles/base.mk
    _walk = $(if $1,$(wildcard /$(subst $(sp),/,$1)/$2) $(call _walk,$(wordlist 2,$(words $1),x $1),$2))
    _find = $(firstword $(call _walk,$(strip $(subst /, ,$1)),$2))
    PROJECT_ROOT := $(patsubst %/$(anchor),%,$(call _find,$(CURDIR),$(anchor)))
endif

anchor is just a file existing in your project, could be something dummy, could be something important.

PROJECT_ROOT is the absolute path of your project root directory.

2nd, find out the working directory and corresponding output directory

If cd PROJECT_ROOT/src/mod1 && make, then working directory is PROJECT_ROOT/src/mod1.

If make -C PROJECT_ROOT/src/tool1, then working directories is PROJECT_ROOT/src/tool1.

LAST_MAKEFILE := $(lastword $(MAKEFILE_LIST))
WORKING_DIR := $(patsubst %/,%,$(dir $(abspath $(LAST_MAKEFILE))))

RELATIVE_WORKING_DIR := $(patsubst $(PROJECT_ROOT)/%,%,$(WORKING_DIR))
OUTPUT_DIR := $(PROJECT_ROOT)/output/$(RELATIVE_WORKING_DIR)

3rd, write rules with absolute path

Example for C project.

$(OUTPUT_DIR)/%.d: $(WORKING_DIR)/%.c
	set -e; rm -f $@; $(CC) -I$(PROJECT_ROOT)/headers -M $(CFLAGS) $< > $@.$$$$; sed 's,\($*\)\.o[ :]*,$(OUTPUT_DIR)/\1.o $@ : ,g' < $@.$$$$ > $@; rm -f $@.$$$$

$(OUTPUT_DIR)/%.o : $(WORKING_DIR)/%.c $(OUTPUT_DIR)/%.d
	$(COMPILE.c) -Wall -g -std=c99 -pedantic -I$(PROJECT_ROOT)/headers -o $@ $<

Implementation for C project on Linux

Document: Paint for C on Linux