DEVELOPMENT TOOLS
• Compilers. A compiler translates the source code to target code. The target code may be the machine language for a particular platform or embedded device. The target code could be another source language; for example, the earliest C++ compiler translated C++ into C, another higher-level language. The resulting C code was then processed by a C compiler to produce an executable program. C++ compilers today translate C++ directly into machine language.
The complete set of build tools for C++ includes a preprocessor, compiler, and linker:
– Preprocessor—adds to or modifies the contents of the source file before the compiler begins
processing the code. We use the services of the preprocessor mainly to #include information
about library routines our programs use.
– Compiler—translates C++ source code to machine code.
– Linker—combines the compiler-generated machine code with precompiled library code or compiled code from other sources to make a complete executable program. Most compiled C++ code is incapable of running by itself and needs some additional machine code to make a complete executable program. The missing machine code has been precompiled and stored in a repository of code called a library. A program called a linker combines the programmer’s compiled code and the library code to make a complete program.
We generally do not think about the preprocessor, compiler, and linker working as three separate programs (although they do); the tools we use make it appear as only one process is taking place: translating our source code to an executable program.
• Debuggers. A debugger allows a programmer to more easily trace a program’s execution in order to locate and correct errors in the program’s implementation. With a debugger, a developer can simultaneously run a program and see which line in the source code is responsible for the program’s current actions. The programmer can watch the values of variables and other program elements to see if their values change as expected. Debuggers are valuable for locating errors (also called bugs) and repairing programs that contain errors.
• Profilers. A profiler collects statistics about a program’s execution allowing developers to tune appropriate parts of the program to improve its overall performance. A profiler indicates how many times a portion of a program is executed during a particular run, and how long that portion takes to execute. Profilers also can be used for testing purposes to ensure all the code in a program is actually being used somewhere during testing. This is known as coverage. It is common for software to fail after its release because users exercise some part of the program that was not executed anytime during testing. The main purpose of profiling is to find the parts of a program that can be improved to make the program run faster.
