C Error Exception
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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 embedded filesystem component
Exception Handling In C Language
of On Time RTOS-32, our Win32-compatible RTOS for 32-bit x86 targets. The core filesystem is portable c exception handling best practices with a C function API to the application and a device-driver interface below it. Typically, errors can occur in device drivers and must c throw error 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 a value indicating success or failure. However,
Exception Handling In C Sharp
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 been a nightmare to maintain. Programming languages such as Ada
Error Handling In C++
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 how we designed and implemented our exception-handling library, demonstrate how it is used, and compare it to C++ exception handling.
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Handler.h In C
x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join c setjmp them; it only takes a minute: Sign up How to throw an exception in C? up vote 41 down vote favorite 4 I typed this into google but only found howtos in C++, how to do it in C? c http://www.on-time.com/ddj0011.htm exception syntax share|improve this question asked May 23 '10 at 12:48 httpinterpret 1,30251931 3 C doesn't support exception handling. To throw an exception in C, you need to use something platform specific such as Win32's structured exception handling -- but to give any help with that, we'll need to know the platform you care about. –Jerry Coffin May 23 '10 at 12:49 10 ...and don't use Win32 structured exception handling. –Brian R. Bondy May 23 '10 at http://stackoverflow.com/questions/2891766/how-to-throw-an-exception-in-c 12:52 1 Using setjmp() and longjmp() should, in theory, work, but I don't think it is worth the trouble. –Joseph Quinsey May 23 '10 at 13:37 14 Use C to write a C++ compiler, then write C++ code to throw an exception. 8-)} –Keith Thompson Jul 3 '13 at 20:51 add a comment| 10 Answers 10 active oldest votes up vote 27 down vote There are no exceptions in C. Exceptions defined in C++ and other languages though. Exception handling in C++ is specified in the C++ standard "S.15 Exception handling", there is no equivalent section in the C standard. share|improve this answer answered May 23 '10 at 12:49 Brian R. Bondy 197k82472571 2 So in C it's guaranteed there won't be exceptions,how? –httpinterpret May 23 '10 at 12:55 23 @httpinterpret: in C it's "guaranteed" that there are no exceptions in the same way that it's "guaranteed" that there are no templates, or no reflection, or no unicorns. The language specification simply doesn't define any such thing. There is setjmp/longjmp, though, which can be used to exit a function without returning. So programs could build their own exception-like mechanisms if they want, or a C implementation could define extensions to the standard. –Steve Jessop May 23 '10 at 17:38 1 A program with main in a .c file can include some C++, and therefore exceptions could be thrown and caught
to be really useful in practice but it is a useful lesson about longjump and setjump with a fun example. Introduction Exception are a very powerful way to program error safe programs. Exceptions let you http://www.di.unipi.it/~nids/docs/longjump_try_trow_catch.html write straight code without testing for errors at each statement. In modern programming languages, such as C++, Java or C#, exceptions are expressed with the try-throw-catch statement. ... try { ... /* error prone statements */ ... } catch(SomeExceptionType e) { ... /* do something intelligent here*/ ... } ... In previous example every exception raised by operations performed in try-block is passed to the right catch-black. If the exception type match SomeExceptionType than in c the code in that block is executed. Otherwise the exception is passed to the try-block that contains the actual one (if any). Our solution is not a fully functional try-throw-catch system. It does not forward exceptions from one block to one more external if no handler is provided. Real exception mechanisms need run-time support. We only want to explore the potentiality of longjmp and setjmp function with a non trivial example. Longjmp And SetJmp ANSI-C handling in c provide a lot of functions: math functions (log, sqrt...), string handling functions (strdup, strcmp, ...) and I/O functions (getc, printf, ...). All these functions are widely used and simple to understand (...strtok is not so intuitive after all...): only two functions are considered strange beasts. These functions are longjmp and setjmp. longjmp and setjmp are defined in setjmp.h header file... #include