Laboratory Exercises, C++ Programming

More documents

Recommendations

Info

14 Tools for Practical C++ Development 1.3 Rules for Linking In our example makefile, we used an explicit rule for linking. Actually, there is an implicit rule for linking, which looks (after some variable expansions) like this: $(CC) $(LDFLAGS) $^ $(LOADLIBES) $(LDLIBS) -o $@ LDFLAGS are options to the linker, such as -Ldirectory. LOADLIBES and LDLIBS 6 are variables intended to contain libraries, such as -llab1. So this is a good rule, except for one thing: it uses $(CC) to link, and CC is by default gcc, not g++. But if you change the definition of CC, the implicit rule works also for C++: # Define the linker CC = g++ 1.4 Generating Prerequisites Automatically While you’re working with a project the prerequisites are often changed. New #include directives are added and others are removed. In order for make to have correct information of the dependencies, the makefile must be modified accordingly. The necessary modifications can be performed automatically by make itself. A3. Read the make manual, section 4.14 “Generating Prerequisites Automatically”, and implement such functionality in your makefile. Hint: Copy the %.d rule (it is not necessary that you understand everything in it) to your makefile and make suitable modifications. Do not forget to include the *.d files. The first time you run make you will get a warning about .d files that don’t exist. This is normal and not an error. Look at the .d files that are created and see that they contain the correct dependencies. One useful make facility that we haven’t mentioned earlier is wildcards: as an example, you can define the variable SRC as a list of all .cc files with SRC = $(wildcard *.cc). And from this you can get all .o files with OBJ = $(SRC:.cc=.o). From now on, you must update the makefile when you add new programs, so that you can always issue the make command in the build directory to build everything. When you add a new program, you should only have to add a rule that defines the .o-files that are necessary to link the program, and maybe add the program name to a list of executables. This is important — it will save you many hours of command typing. (Optional) Collect all object files not containing main functions into a library, and link executables against that library. If you know how to create shared libraries, use a shared library libcxx.so, otherwise create a static archive libcxx.a. 1.5 Writing a Good Makefile A makefile should always be written to run in sh (Bourne Shell), not in csh. Do not use special features from, e.g., bash, zsh, or ksh. The tools used in explicit rules should be accessed through make variables, so that the user can substitute alternatives to the defaults. A makefile should also be written so that it doesn’t have to be located in the same directory as the source code. You can achieve this by defining a SRCDIR variable and make all rules refer to the source code from that prefix. Even better is to use the variable VPATH, which specifies a search path for source files. Vpath is described in section 4.5 of the make manual. 6 There doesn’t seem to be any difference between LOADLIBES and LDLIBS — they always appear together and are concatenated. Use LDLIBS.
Tools for Practical C++ Development 15 A4. (Optional, VPATH is difficult) Create a new directory, src, for C++ lab source code and copy the source files from lab 1 into it. In a parallel directory build, install the Makefile, and modify it so that you can build the programs (and possibly libraries), standing in the build directory. The all target, which should be default, should build your ltest, encode, and decode programs. No command should write to the src directory. 2 Debugging Consider the following program (reciprocal.cc): #include #include // for atoi, see below double reciprocal(int i) { return 1.0 / i; } int main(int argc, char** argv) { int i = std::atoi(argv[1]); // atoi: "ascii-to-integer" double r = reciprocal(i); std::cout
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 12 and 13: 12 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

Create successful ePaper yourself

Delete template?

Save as template?