C++ Programming

C++ Programming HOW-TO Al Dev (Alavoor Vasudevan) alavoor@yahoo.com v16.0, 03 Aug 2000 This document discusses methods to avoid memory problems in C++ and also will help you to program properly in C++ language. The informa? tion in this document applies to all the operating systems that is - Linux, MS DOS, BeOS, Apple Macintosh OS, Microsoft Windows 95/98/NT/2000, OS/2, IBM OSes (MVS, AS/400 etc..), VAX VMS, Novell Netware, all flavors of Unix like Solaris, HPUX, AIX, SCO, Sinix, BSD, etc.. and to all other operating systems which support "C++" compiler (it means almost all the operating systems on this planet!). ______________________________________________________________________ Table of Contents 1. Introduction 1.1 Problems facing the current C++ compilers 1.2 Which one "C", "C++" or Java ? 2. Download String 3. Usage of String class 3.1 Operators 3.2 Functions 4. C++ Zap (Delete) command 5. Pointers are problems 6. Usage of my_malloc and my_free 7. Debug files 8. C++ Online-Docs 8.1 C++ Tutorials 8.2 C++ Coding Standards 8.3 C++ Quick-Reference 8.4 C++ Usenet Newsgroups 9. Memory Tools 10. Related URLs 11. Other Formats of this Document 12. Copyright 13. Appendix A example_String.cpp 14. Appendix B String.h 15. Appendix C String.cpp 16. Appendix D my_malloc.cpp 17. Appendix E my_malloc.h 18. Appendix F debug.h 19. Appendix G debug.cpp 20. Appendix H Makefile ______________________________________________________________________ 1. Introduction C++ is the most popular language and will be used for a long time in the future inspite of emergence of Java. C++ runs extremely fast and is in fact 10 to 20 times FASTER than Java. Java runs very slow because it is an byte-code-interpreted language running on top of "virtual machine". Java runs faster with JIT compiler but is still slower than C++. And optimized C++ program is about 3 to 4 times faster than Java using the JIT (Just-In-Time) compiler!! The memory management in Java is automated, so that programmers do not directly deal with memory allocations. This document attempts to automate the memory management in C++ to make it much more easy to use. A neat feature of Java is that memory allocations are taken care of automatically. This howto will enable "C++" to "compete/imitate" with Java language in memory management. Because of manual memory allocations, debugging the C++ programs consumes a major portion of time. The information in this document will give you some better ideas and tips to reduce the debugging time. 1.1. Problems facing the current C++ compilers Since C++ is super-set of C, it got all the bad features of "C" language. For example, in "C" programming - memory leaks, memory overflows are very common due to usage of features like - ______________________________________________________________________ Datatype char * and char[] String functions like strcpy, strcat, strncpy, strncat, etc.. Memory functions like malloc, realloc, strdup, etc.. ______________________________________________________________________ The usage of char * and strcpy causes horrible memory problems due to "overflow", "fence past errors", "step-on-others-toe" (hurting other variable's memory locations) or "memory leaks". The memory problems are extremely hard to debug and are very time consuming to fix and trouble-shoot. Memory problems bring down the productivity of programmers. This document helps in increasing the productivity of programmers via different methods addressed to solve the memory defects in "C++". Memory related bugs are very tough to crack, and even experienced programmers take several days, weeks or months to debug memory related problems. Many times memory bugs will be "hiding" in the code for several months and can cause unexpected program crashes!! The usage of char * in C++ is costing USA and Japan $2 billion every year in time lost in debugging and downtime of programs. If you use char * in C++ then it is a very costly affair especially if your programs have more than 50,000 lines of code. Hence, the following techniques are proposed to overcome the faults of "C" language. It is proposed that C++ compilers should prevent the programmers from using the "char *" , "char[]" datatypes and functions like strcpy, strcat, strncpy, strncat. The datatypes like char *, char[] and functions like strcpy, strcat are evil and must be completetly BANNED from usage in C++!! The "char *" is like smallpox virus and it must be eradicated from C++ world!! If you want to use "char *" as in some system functions than you should use "C" language. You would put all your "C" programs in a separate file and link to "C++" programs using the linkage-specification statement extern "C" - ______________________________________________________________________ extern "C" { #include <stdlib.h> } extern "C" { comp(); some_c_function(); } ______________________________________________________________________ The extern "C" statement says that everything within the brace-sur? rounded block - in this case, everything in the header file and comp(), some_c_function() is compiled by a C compiler. Instead of using char * and char[] all the C++ programmers MUST use the which is given in this document and included in the STDLIB. The utilises the constructor and destructor to automate the memory management and also provides many functions like ltrim, substring, etc.. See also related in the C++ compiler. The string class is part of the standard GNU C++ library and provides lot of string manipulation functions. The can remove the need of char * datatype. Also, C++ programmers must be encouraged to use 'new', 'delete' features instead of using 'malloc' or 'free'. The does everything that char * or char [] does. It can completely replace char datatype. Plus added benefit is that programmers do not have to worry about the memory problems and memory allocation at all!! The GNU C++ compiler MUST drop off the support of char *, char[] datatypes and in order to compile older programs using char datatype, the compiler should provide a additional option called "-fchar- datatype" to g++ command. Over the next 2 years all the C++ programs will use and and there will be no char * and char[]. The compiler should try to prevent bad programming practices! 1.2. Which one "C", "C++" or Java ? It is recommended you do programming in object-oriented "C++" for all your application programming or general purpose programming. You can take full advantage of object oriented facilities of C++. The C++ compiler is lot more complex than "C" compiler and C++ programs may run bit slower than "C" programs. But speed difference between "C" and "C++" is very minute - it could be few milli-seconds which may have little impact for real-time programming. Since computer hardware is becoming cheaper and faster and memory "C" as time saved in clarity and re-usability of C++ code offsets the slow speed. Compiler optimizer options like -O or -O3 can speed up C++/C which is not available in Java. Nowadays, "C" language is primarily used for "systems programming" to develop operating systems, device drivers etc.. Note: Using the String, StringBuffer, StringTokenizer and StrinReader classes given in this howto, you can code in C++ which "exactly" looks like Java!! This document tries to close the gap between C++ and Java, by imitating Java classes in C++