Make

make is an utility that determines automatically which pieces of a program need to be recompiled, and issues the commands to rebuild them. make uses a file called Makefile, which describes the relationships among files in the program.

References

• GNU 'Make'
  • Manual

Tips

Automatic Prerequisites

A standard solution (inspired from Makefile manual):

#----- BEGIN Automatic-Prerequisites -----
# - see http://www.gnu.org/software/make/manual/make.html#Automatic-Prerequisites
# - Note that .d files are automatically regenerated because of the include command below.
# - Only 1 .d file generated, indep. of defines. So if include files depend on defines, the .d files will *NOT* be updated.

-include $(SOURCES:.cpp=.d)

%.d: %.cpp
	@set -e; rm -f $@; \
	$(CC) $(CFLAGS) $(INCPATHS) -MM $< | sed -r 's!(.*)\.o[ :]*!\1.o $@ : !g' > $@
#----- END Automatic-Prerequisites -----

A more advanced solution, where object files are stored in directory $(VARDIR), and have a suffic $(VARIANT):

#----- BEGIN Automatic-Prerequisites -----
# - see http://www.gnu.org/software/make/manual/make.html#Automatic-Prerequisites
# - Note that .d files are automatically regenerated because of the include command below.
# - Only 1 .d file generated, indep. of defines. So if include files depend on defines, the .d files will *NOT* be updated.
# - [CHANGES] .o and .d files are stored in directory $(VARDIR)/, and have suffix $(VARIANT)

-include $(addprefix $(VARDIR)/, $(notdir $(SOURCES:.cpp=.d) ) )

$(VARDIR)/%.d: $(SRCDIR)/%.cpp
	@mkdir -p "$(@D)"; \
	set -e; rm -f $@; \
	$(CPP) $(CFLAGS) $(INCPATHS) -MM -MT $(VARDIR)/$*.o $< | sed 's!\(.*\)\.o[ :]*!\1$$(VARIANT).o $@ : !g' > $@
#----- END Automatic-Prerequisites -----

Limitations:

• Only one .d file generated, indep. of $(DEFINES), so if $(DEFINES) changed, and include files depends on these defines, the .d files will not be updated.

A solution would be to name the .d files according to relevant defines, as we do for the .o files

Frequent Mistakes

Use TABS to prefix commands in rules, *NOT* SPACES

Each rule in a makefile gives the set of commands that must be executed to build a given target from a given set of dependencies. These commands MUST be indented with a TAB character, not with SPACES. So make sure that the editor does not automatically change these tabs into spaces.