Laboratory Exercises, C++ Programming

More documents

Recommendations

Info

12 Tools for Practical C++ Development ltest.o: ltest.cc list.h On the line following the dependency specification you write a shell command that generates the target. This is called an explicit rule. Example (with a short command line without options): ltest.o: ltest.cc list.h g++ -c ltest.cc Make has a very unusual syntax requirement: the shell command must be preceded by a tab character; spaces are not accepted. An implicit rule does not give an explicit command to generate the target. Instead, it relies on make’s large collection of default rules. For instance, make knows how to generate .o-files from most kinds of source files, for instance that g++ is used to generate .o-files from .cc-files. The actual implicit rule is: $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $< CXX, CPPFLAGS, and CXXFLAGS are variables that the user can define. The syntax $(VARIABLE) is used to evaluate a variable, returning its value. CXX is the name of the C++ compiler, CPPFLAGS are the options to the preprocessor, CXXFLAGS are the options to the compiler. $@ expands to the name of the target, $< expands to the first of the prerequisites. We are now ready to write our first makefile, which will build the ltest program from lab 1. The value g++ for CXX is default, thus that definition is optional. CPPFLAGS and CXXFLAGS are empty by default. CXXFLAGS is almost always redefined. # Compiler and compiler options: CXX = g++ CXXFLAGS = -pipe -O2 -Wall -W -ansi -pedantic-errors CXXFLAGS += -Wmissing-braces -Wparentheses -Wold-style-cast # Linking: ltest: ltest.o list.o $(CXX) -o $@ $^ # Dependencies, the implicit rule .cc => .o is used: ltest.o: ltest.cc list.h list.o: list.cc list.h $^ expands to the complete list of prerequisites. We will make improvements to this makefile later. Suppose that none of the files ltest, ltest.o, list.o exists. Then, the following commands are executed when you run make (the long command lines have been wrapped): make ltest g++ -pipe -O2 -Wall -W -ansi -pedantic-errors -Wmissing-braces -Wparentheses -Wold-style-cast -c -o ltest.o ltest.cc g++ -pipe -O2 -Wall -W -ansi -pedantic-errors -Wmissing-braces -Wparentheses -Wold-style-cast -c -o list.o list.cc g++ -o ltest ltest.o list.o If an error occurs in one of the commands, make will be aborted. If there, for instance, is an error in list.cc, the compilation of that file will be aborted and the program will not be linked. When you have corrected the error and run make again, it will discover that ltest.o is up to date and only remake list.o and ltest. If you run make without a target name as parameter, make builds the first target it finds in the
Tools for Practical C++ Development 13 makefile. Since ltest is the first target, make ltest and make are equivalent. By convention, the first target should be named all. Therefore, the first rules in the makefile should look like this: # Default target ‘all’, make everything all: ltest # Linking: ltest: ltest.o list.o $(CXX) -o $@ $^ Makefiles can also contain directives that control the behavior of make. For example, a makefile can include other files with the include directive. A1. The file Makefile contains the makefile that has been used as an example. Experiment with make: copy the necessary source files (list.h, list.cc and ltest.cc) to the lab2 directory and run make. Run make again. Delete the executable program and run make again. Change one or more of the source files (it is sufficient to touch them) and see what happens. Run make ltest.o. Run make notarget. Read the manpage and try other options. Etc., etc. 1.2 Phony targets Makefiles may contain targets that do not actually correspond to files. The all target in the previous section is an example. Now, suppose that a file all is created in the directory that contains the makefile. If that file is newer than the ltest file, a make invocation will do nothing but say make: Nothing to be done for ‘all’., which is not the desired behavior. The solution is to specify the target all as a phony target, like this: .PHONY: all Another common phony target is clean. Its purpose is to remove intermediate files, such as object files, and it has no prerequisites. It typically looks like this: .PHONY: clean clean: $(RM) $(OBJS) The variable RM defaults to rm -f, where the option -f tells rm not to warn about non-existent files. The return value from the command is always 0, so the clean target will always succeed. A cleaning rule that removes also executable files and libraries could be called, e.g., cleaner or realclean. All Unix source distributions contain one or more makefiles. A makefile should contain a phony target install, with all as its prerequisite. The make install command copies the programs and libraries built by the all rule to a system-wide location where they can be reached by other users. This location, which is called the installation prefix, is usually the directory /usr/local. Installation uses the GNU command install (or plain cp) to copy programs to $(PREFIX)/bin and libraries to $(PREFIX)/lib. Since only root has permission to write in /usr/local, you will have to use one of your own directories as prefix. A2. Create the bin and lib directories. Add all, clean and install targets to your makefile and specify suitable phony targets. Also provide an uninstall target that removes the files that were installed by the install target.
Page 1: LUND INSTITUTE OF TECHNOLOGY C++ Pr
Page 4 and 5: 4 The GNU Compiler Collection and C
Page 10 and 11: 10 The GNU Compiler Collection and
Page 14 and 15: 14 Tools for Practical C++ Developm
Page 24 and 25: 24 Strings and Streams char type is
Page 26 and 27: 26 Strings and Streams A2. The Siev
Page 28 and 29: 28 Strings and Streams A3. The file
Page 30 and 31: 30 Programming with the STL find_if
Page 32 and 33: 32 Programming with the STL An outl

Laboratory Exercises, C++ Programming

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?