C Error Handling Class
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Peter Petersen Error handling is an important issue in embedded systems, and it can account for a substantial portion of a project's code. We were faced with this issue during the design of RTFiles, the php error handling class embedded filesystem component of On Time RTOS-32, our Win32-compatible RTOS for 32-bit x86 targets. The objective c error handling core filesystem is portable with a C function API to the application and a device-driver interface below it. Typically, errors can occur
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in device drivers and must be reported to the application with suitable return codes, so errors must travel through the complete core filesystem. The classic C approach to this problem is return codes. Each function returns
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a value indicating success or failure. However, with a nontrivial function call hierarchy, this approach clutters the code significantly. Every function must check the return code of every function call it makes and take care of errors. In most cases, the function will merely pass any errors back up to its caller. RTFiles has several hundred internal functions and a call hierarchy up to about 15 levels deep, so this approach would have c++ error handling without exceptions been a nightmare to maintain. Programming languages such as Ada or C++ address this issue with exceptions. Exceptions make it easy to separate error handling from the rest of the code. Intermediate functions can completely ignore errors occurring in functions they call, if they can't handle them anyway. Exceptions are much easier to maintain than error return codes, so we definitely wanted to use them for RTFiles. Unfortunately, we had to write RTFiles in C, and not C++ or Ada, for portability. RTFiles must support compilers without C++ support. Another issue is overhead and reliability. C++ exception handling needs a lot of run-time system support routines, which might add too much code to a small embedded system. C++ exceptions are objects dynamically allocated from the heap, but many embedded systems do not want to use any dynamic memory allocation to avoid heap fragmentation and out-of-heap-space problems. For example, what would happen if an RTFiles device driver throws a disk-write-protection exception, and the heap allocation called by throw throws an out-of-memory exception? The solution to the problem is to implement a simple exception-handling library in C with the following goals: No dynamic memory allocation. Robust (the exception handling library itself must not fail). Must support both exception-handlers and finally-handlers. Reentrant for multitasking applications. In this article, we describe
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Strings C - Structures C - Unions C - Bit Fields C - Typedef C - ruby error handling Input & Output C - File I/O C - Preprocessors C - Header Files C - Type Casting C - Error Handling C - exception handling in c language Recursion C - Variable Arguments C - Memory Management C - Command Line Arguments C Programming Resources C - Questions & Answers C - Quick Guide C - Useful Resources C - Discussion Selected Reading Developer's Best Practices Questions and http://www.on-time.com/ddj0011.htm Answers Effective Resume Writing HR Interview Questions Computer Glossary Who is Who C - Error Handling Advertisements Previous Page Next Page As such, C programming does not provide direct support for error handling but being a system programming language, it provides you access at lower level in the form of return values. Most of the C or even Unix function calls return -1 or NULL in case of any error and set an error code errno. It is set https://www.tutorialspoint.com/cprogramming/c_error_handling.htm as a global variable and indicates an error occurred during any function call. You can find various error codes defined in
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Practice Problems Quizzes Resources Source Code Source Code Snippets C and C++ Tips Finding a Job References Function Reference Syntax Reference Programming FAQ Getting Help Message Board Email About Us Handling Errors Exceptionally Well in C++ By Alex Allain One benefit of C++ over C is its exception handling system. An exception is a situation in which a program has an unexpected circumstance that the section of code containing the problem is not explicitly designed to handle. In C++, exception handling is useful because it makes it easy to separate the error handling code from the code written to handle the chores of the program. Doing so makes reading and writing the code easier. Furthermore, exception handling in C++ propagates the exceptions up the stack; therefore, if there are several functions called, but only one function that needs to reliably deal with errors, the method C++ uses to handle exceptions means that it can easily handle those exceptions without any code in the intermediate functions. One consequence is that functions don't need to return error codes, freeing their return values for program logic. When errors occur, the function generating the error can 'throw' an exception. For example, take a sample function that does division: const int DivideByZero = 10; //.... double divide(double x, double y) { if(y==0) { throw DivideByZero; } return x/y; } The function will throw DivideByZero as an exception that can then be caught by an exception-handling catch statement that catches exceptions of type int. The necessary construction for catching exceptions is a try catch system. If you wish to have your program check for exceptions, you must enclose the code that may have exceptions thrown in a try block. For example: try { divide(10, 0); } catch(int i) { if(i==DivideByZero) { cerr<<"Divide by zero error"; } } The catch statement catches exceptions that are of the proper type. You can, for example, throw objects of a class to differentiate between several different exceptions. As well, once a catch statement is executed, the program continues to run from the end of the catch. It is often more useful for you to create a class that stores information on exceptions as they occur. For ex