Checking Error In C
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- Error Handling C - 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 c atoi error checking Selected Reading Developer's Best Practices Questions and 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 error checking in c programming any error and set an error code errno. It is set 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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Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it https://www.tutorialspoint.com/cprogramming/c_error_handling.htm only takes a minute: Sign up Error handling in C code up vote 102 down vote favorite 59 What do you consider "best practice" when it comes to error handling errors in a consistent way in a C library. There are two ways I've been thinking of: Always return error code. A typical function would look like this: MYAPI_ERROR getObjectSize(MYAPIHandle http://stackoverflow.com/questions/385975/error-handling-in-c-code h, int* returnedSize); The always provide an error pointer approach: int getObjectSize(MYAPIHandle h, MYAPI_ERROR* returnedError); When using the first approach it's possible to write code like this where the error handling check is directly placed on the function call: int size; if(getObjectSize(h, &size) != MYAPI_SUCCESS) { // Error handling } Which looks better than the error handling code here. MYAPIError error; int size; size = getObjectSize(h, &error); if(error != MYAPI_SUCCESS) { // Error handling } However, I think using the return value for returning data makes the code more readable, It's obvious that something was written to the size variable in the second example. Do you have any ideas on why I should prefer any of those approaches or perhaps mix them or use something else? I'm not a fan of global error states since it tends to make multi threaded use of the library way more painful. EDIT: C++ specific ideas on this would also be interesting to hear about as long as they are not involving exceptions since it's not an option for me at the mo
EOF that is defined for that purpose. But this return value tells you only that an error has occurred. To find http://www.gnu.org/s/libc/manual/html_node/Checking-for-Errors.html out what kind of error it was, you need to look at the error code stored in the variable errno. This variable is declared in the header file errno.h. Variable: volatile int errno The variable errno contains the system error number. You can change the value of errno. Since errno is declared volatile, it might be changed asynchronously by in c a signal handler; see Defining Handlers. However, a properly written signal handler saves and restores the value of errno, so you generally do not need to worry about this possibility except when writing signal handlers. The initial value of errno at program startup is zero. Many library functions are guaranteed to set it to certain nonzero values when they c error handling encounter certain kinds of errors. These error conditions are listed for each function. These functions do not change errno when they succeed; thus, the value of errno after a successful call is not necessarily zero, and you should not use errno to determine whether a call failed. The proper way to do that is documented for each function. If the call failed, you can examine errno. Many library functions can set errno to a nonzero value as a result of calling other library functions which might fail. You should assume that any library function might alter errno when the function returns an error. Portability Note: ISOC specifies errno as a “modifiable lvalue” rather than as a variable, permitting it to be implemented as a macro. For example, its expansion might involve a function call, like *__errno_location(). In fact, that is what it is on GNU/Linux and GNU/Hurd systems. The GNU C Library, on each system, does whatever is right for the particular system. There are a few library functions, like sqrt and atan, that retu