magic.mk

magic.mk is a tiny file that handles build dependencies and profiles without any meta-build system convolution.

Manual

The following is a guide on using magic.mk which references the example Makefile included in this repository.

SRC := test/hello.c test/plusplus.c

SRC is set to a list of translation units that should be compiled. magic.mk creates rules for compiling each file in SRC to an object file.

BUILDDIR := obj
MAGIC_DEFAULT_PROFILE := debug

BUILDDIR sets the directory that will be used for build files. Each profile will have its own subdirectory in here unless defined otherwise with PROFILEDIR. If undefined, this is set to "build".
MAGIC_DEFAULT_PROFILE specifies the profile that will be used if make is called without a target argument.

define PROFILE.debug
  MAGIC_TARGET := build
  CFLAGS += -g
endef

Profiles are defined using PROFILE.[profile name]. The text inside a profile definition is evaluated only when that profile is targeted.
MAGIC_TARGET is the actual target that will be run by make for this profile.

define PROFILE.clean
  MAGIC_NODEP := 1
endef

The "clean" profile does not define MAGIC_TARGET. "clean" is a real target in the Makefile already, so it does not need to be forwarded.
MAGIC_NODEP specifies that this profile does not care about dependencies. Otherwise, dependency information would could be wastefully generated and immediately deleted.

define PROFILE.run
  $(PROFILE.debug)
  PROFILEDIR := debug
endef

Like "clean", run is a real target so the target is not forwarded.
"run" needs the debug executables, so it inherits the "debug" profile.
PROFILEDIR is explicitly set to debug, otherwise the "run" profile would be built in a new directory which would be unnecessary.

include magic.mk

After the profiles are defined magic.mk can be included.
After it has been included, the chosen profile has been evaluated, and new variables are defined.
OBJ is the list of object files that correspond to SRC.
OBJDIR is the location in which the objects will be stored.
PROFILE is the name of the profile that was evaluated.