Laboratory Exercises, C++ Programming

Tools for Practical C++ Development 11
2 Tools for Practical C++ Development
Objective: to introduce a set of tools which are often used to facilitate C++ development in a Unix
environment. The make tool (GNU Make) is used for compilation and linking, gdb (the GNU
debugger) for controlled execution and testing, valgrind (not GNU) for finding memory-related
errors.
Read:
• GNU Make, http://www.gnu.org/software/make/manual/
• GDB User Manual, http://www.gnu.org/software/gdb/documentation/
• valgrind Quick Start, http://www.valgrind.org/docs/manual/QuickStart.html
• Manpages for the tools used in the lab.
The manuals have introductory tutorials that are recommended as starting points. The manuals
are very well written and you should consult them if you want to learn more than what is treated
during the lab.
1 GNU Make
1.1 Introduction
As you saw in lab 1, make is a good tool — it sees to it that only files that have been modified
are compiled (and files that depend on modified files). To do this, it compares the modification
times 5 of source files and object files.
We will use the GNU version of make. There are other make programs, which are almost but
not wholly compatible to GNU make. In a Linux or Darwin system, the command make usually
refers to GNU make. You can check what variant you have with the command make --version.
It should give output like the following:
make --version
GNU Make 3.81
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
...
If make turns out to be something else than GNU make, try the command gmake instead of make;
this should refer to GNU make.
Make uses a description of the source project in order to figure out how to generate executables.
The description is written in a file, usually called Makefile. When make is executed, it reads
the makefile and executes the compilation and linking (and maybe other) commands that are
necessary to build the project.
The most important construct in a makefile is a rule. A rule specifies how a file (the target),
which is to be generated, depends on other files (the prerequisites). For instance, the following
rule specifies that the file ltest.o depends on the files ltest.cc and ltest.h:
5 In a network environment with a distributed file system, there may occur problems with unsynchronized clocks
between a client and the file server. Make will report errors like:
make: ***Warning: File "foo" has modification time in the future.
make: warning: Clock skew detected. Your build may be incomplete.
Unfortunately, there is not much you can do about this problem, if you don’t have root privileges on the computer.
Inform the system administrators about the problem and switch to another computer if possible. If no other computer is
available, temporarily work on a local file system where you have write access, such as /tmp.