Build systems



From the documentation are indicated some standard targets like all, install, clean etc...

The default target (when one is not indicated) is the first defined in the Makefile if .DEFAULT_GOAL is not set.

A particular type of target is a phony target, i.e. a target that doesn't reflect an actual file on the filesystem.

The syntax of a target is the following

<targets>: <normal-prerequisites> | <order-only-prerequisites>


Exists substitution references (see doc)in the form of $(var:a=b) where the value of the variable var has the occurrence of the a at the end of it replaced with b; for example $(SOURCE:%.c=%.o) is the quick way to obtain the corresponding derived object filename from source files.

Automatic variables

See doc:

  • $@: target
  • $<: first prerequisite
  • $?: all prerequisites newer than the target
  • $^: all the prerequisites (listed only one each)
  • $+: all the prerequisites (listed multiple time if it's the case)
  • $|: all the order-only prerequisites
  • $*: the stem with which an implicit rule matches

Predefined variables

There are a certain number of variables that you can use into predefined target rules, like compiling C code and so on.

  • LDFLAGS: Extra flags to give to compilers when they are supposed to invoke the linker, ld, such as -L. Libraries (-lfoo) should be added to the LDLIBS variable instead.

  • LDLIBS: Library flags or names given to compilers when they are supposed to invoke the linker, ld. LOADLIBES is a deprecated (but still supported) alternative to LDLIBS. Non-library linker flags, such as -L, should go in the LDFLAGS variable.

    @echo $(if $(need-help),,Type \'$(MAKE)$(dash-f) help\' to get help)

need-help := $(filter help,$(MAKECMDGOALS))

define print-help
$(if $(need-help),$(warning $1 -- $2))

define last-element
$(word $(words $1),$1)

this-makefile := $(call last-element,$(MAKEFILE_LIST))
other-makefiles := $(filter-out $(this-makefile),$(MAKEFILE_LIST))
parent-makefile := $(if other-makefiles,,$(call last-element,$(other-makefiles)))

dash-f := $(if $(filter-out Makefile makefile GNUmakefile,$(parent-makefile)), -f $(parent-makefile))


$ CC=gcc CXX=g++ cmake ..

It's possible to indicate variable like the following

$ cmake -DUSE_QT5=1 -DCMAKE_BUILD_TYPE=Debug ..

If you want a verbose output for the Makefile generated, you can use make VERBOSE=1