You wish to use GNU make to build a dynamic library from a collection of C++ source files, such as those listed in Example 1-2.
First, create a makefile in the directory where you want your dynamic library to be
created, and declare a phony target all
whose single
prerequisite is the dynamic library. Next, declare your dynamic library target. Its
prerequisites should be the object files from which the library will be built, and its
command script should be a command line to build the library from the collection of object
files, as demonstrated in Recipe 1.4. If
you are using GCC or a compiler with similar command-line syntax, customize the implicit
patterns rules, if necessary, by modifying one or more of the variables CXX
, CXXFLAGS
,
etc. used in make's database
of implicit rules, as shown in Recipe
1.15. Otherwise, write a pattern rule telling make how to compile .cpp files into
object files, using the command lines from Table 1-4 and the pattern rule syntax explained in Recipe 1.16. Finally, add install
and clean
targets,
as demonstrated in Recipe 1.15, and
machinery to automatically generate source file dependencies, as demonstrated in Recipe 1.16.
For example, to build a dynamic library from the source files listed Example 1-2 using GCC on Unix, create a makefile in the directory georgeringo, as shown in Example 1-22.
Example 1-22. Makefile for libgeorgeringo.so using GCC
# Specify extensions of files to delete when cleaning CLEANEXTS = o so # Specify the source files, the target files, # and the install directory SOURCES = george.cpp ringo.cpp georgeringo.cpp OUTPUTFILE = libgeorgeringo.so INSTALLDIR = ../binaries .PHONY: all all: $(OUTPUTFILE) # Build libgeorgeringo.so from george.o, ringo.o, # and georgeringo.o; subst is the search-and-replace # function demonstrated in Recipe 1.16 $(OUTPUTFILE): $(subst .cpp,.o,$(SOURCES)) $(CXX) -shared -fPIC $(LDFLAGS) -o $@ $^ .PHONY: install install: mkdir -p $(INSTALLDIR) cp -p $(OUTPUTFILE) $(INSTALLDIR) .PHONY: clean clean: for file in $(CLEANEXTS); do rm -f *.$$file; done # Generate dependencies of .ccp files on .hpp files include $(subst .cpp,.d,$(SOURCES)) %.d: %.cpp $(CC) -M $(CPPFLAGS) $< > $@.$$$$; \ sed 's,\($*\)\.o[ :]*,\1.o $@ : ,g' < $@.$$$$ > $@; \ rm -f $@.$$$$
The makefile in Example 1-22 is a straightforward application of the ideas from Recipe 1.4, Recipe 1.15, and Recipe 1.16. The main difference between Example 1-22 and Example 1-20 is the rule for building lingeorgeringo.so from the object files george.o, ringo.o, and georgeringo.o:
$(OUTPUTFILE): $(subst .cpp,.o,$(SOURCES)) $(CXX) -shared -fPIC $(LDFLAGS) -o $@ $^
Here $(OUTPUTFILE)
expands to lingeorgeringo.so
and the
expression $(subst
.cpp,.o,$(SOURCES))
expands to george.o
, ringo.o
, and georgeringo.o
, as illustrated in Recipe 1.16. The command script $(CXX)
-shared
-fPIC
$(LDFLAGS)
-o
$@
$^
is an adaptation of the GCC command line presented
in Table 1-7.
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