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Previous: Procedures and functions Index Next: Preprocessor Retrieved from "https://en.wikibooks.org/w/index.php?title=C_Programming/Error_handling&oldid=2986554" Category: C Programming Navigation menu Personal tools Not logged inDiscussion for this IP addressContributionsCreate accountLog in Namespaces Book Discussion Variants Views The C programming language has two functions that can be used to display a text message that is associated with errno. Also, don’t mix various styles of error handling in one piece of code like others did… –mirabilos Mar 5 '14 at 14:47 4 I certainly agree about not mixing styles. To handle signals, a program needs to use the signal.h header file.

But the question is focused on C and this question is one of the standard, well-known problems with the C language. Such variable indexes error descriptions accessible by the function 'strerror( errno )'. A call to longjmp causes the execution to return to the point of the associated setjmp call. #include #include jmp_buf test1; void tryjump() { longjmp(test1, 3); } int main Why figure out how functionX should handle a null pointer if you can instead insist that the programmer never pass one?

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A typical function would look like this: MYAPI_ERROR getObjectSize(MYAPIHandle 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 james on November 22nd, 2013: cool post amir on December 13th, 2013: union structure typedef union large_integer{ struct{ Dword lowpart; long highpart; }; struct{ Dword lowpart; long highpart; }u; longlong quadpart;} There are two ways I've been thinking of: Always return error code.

share|improve this answer answered Nov 5 '09 at 8:38 Aaron Digulla 203k60362574 2 Add to questions: who is the error message for (e.g. If the file pointer (fp) equals NULL then we print the value of errno (in this case errno will be 2). I know that this example basically describes printf() itself. Error C Function Get Jumping into C++ today! Popular pages Exactly how to get started with C++ (or C) today C Tutorial C++ Tutorial 5 ways you can learn to program faster The

share|improve this answer answered Dec 22 '08 at 11:00 Alnitak 213k42278351 http://www.gnu.org/s/libc/manual/html_node/Error-Reporting.html There are several advantages of using a typedef'ed enum as a return code.

share|improve this answer edited Jun 6 at 18:01 Air 3,77112446 answered Nov 15 '08 at 0:24 Michael Burr 240k30353574 5 My suggestion above is to return the result and have Error C Stack Usage provide a function that converts errors into something human readable. For example: #ifndef __unix__ // __unix__ is typically defined when targetting Unix #error "Only Unix is supported" #endif Related C preprocessor tutorial Want to become a C++ programmer? I think that sounds like the best idea.

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I'm not a fan of global error states since it tends to make multi threaded use of the library way more painful. http://stackoverflow.com/questions/385975/error-handling-in-c-code The perror() function displays the string you pass to it, followed by a colon, a space, and then the textual representation of the current errno value. Print Error C int dividend = 50; int divisor = 0; int quotient; quotient = (dividend/divisor); /* This will produce a runtime error! */ For reasons beyond the scope of this document, you must Bus Error C All Rights Reserved. | Contact TERMS and Privacy Policy UNDER WHICH THIS SERVICE IS PROVIDED TO YOU.

I'm not a huge fan of this way to handle errors. if( c < LAST_ENTRY) { printf(errorDesc[c]); } } share|improve this answer answered Nov 5 '09 at 8:42 Naveen 43.9k34116205 3 Most systems reserve 0 for 'not an error'. Try our newsletter Sign up for our newsletter and get our top new questions delivered to your inbox (see an example). Use a special 'sentinel' return value to indicate an error, such as a negative number (if normal return values cannot be negative) or INT_MAX or INT_MIN if good values cannot be Error C 0007 Faxmaker

Subscribed! Exiting...\n"); exit(-1); } quotient = dividend / divisor; fprintf(stderr, "Value of quotient : %d\n", quotient ); exit(0); } When the above code is compiled and executed, it produces the following result Join them; it only takes a minute: Sign up What is the best way to return an error from a function when I'm already returning a value? Jobs Send18 Whiteboard Net Meeting Tools Articles Facebook Google+ Twitter Linkedin YouTube Home Tutorials Library Coding Ground Tutor Connect Videos Search C Programming Tutorial C - Home C - Overview C

if(ok) { *ok = 0; } } num *= 10; num += string[current_char] - '0'; current_char++; } if (negative) { num = -num; } if(ok) { *ok = 1; } return Error C Preprocessor /lib/cpp Fails Sanity Check The draw back to this approach is not quite knowing the length of the variadic arguments once expanded. How does the user know what this error is?

Of course the programmer needs to prevent errors during coding and should always test the return values of functions called by the program.

A value of 0 indicates that there is no error in the program. go

C Programming/Error handling From Wikibooks, open books for an open world < C Programming Jump to: navigation, search Previous: Procedures and functions Index Next: Preprocessor C does Let’s take a look at an example: #include #include #include extern int errno; int main () { FILE * fp; fp = fopen ("filedoesnotexist.txt", "rb"); if (fp == Error C Interpreter Run Time Error Developer Network Developer Network Developer Sign in MSDN subscriptions Get tools Downloads Visual Studio MSDN subscription access SDKs Trial software Free downloads Office resources SharePoint Server 2013 resources SQL Server 2014

Signals are events raised by the host environment or operating system to indicate that a specific error or critical event has occurred (e.g. If you just print out the error you will not face any problems. The code below fixes this by checking if the divisor is zero before dividing − #include #include main() { int dividend = 20; int divisor = 0; int quotient; If we take a look in the stdlib.h file (on Linux) you will find something like this: /* We define these the same for all machines.

I'm curious about your reasoning on asserts. This example creates a signal handler and raises the signal: #include #include #include static void catch_function(int signal) { puts("Interactive attention signal caught."); } int main(void) { if (signal(SIGINT, Both comments and pings are currently closed. You’re the person that needs to make sure that a program will gracefully terminate and not just CRASH unexpectedly!

E.g. Where necessary the return result should just indicate that an error occurred, with another function being used to find out the exact error. It is set as a global variable and indicates an error occurred during any function call. Program Exit Status It is a common practice to exit with a value of EXIT_SUCCESS in case of program coming out after a successful operation.

This applies to function and argument naming, argument ordering and error handling. The above example is 'safe', wherein you don't have to worry about over flowing some stack allocated buffer with a formatted error message of undefined length. In more complicated implementations, the program might try to handle the error and try to recover from the failed memory allocation. In your getSize() example I'd consider that sizes must always be zero or positive, so returning a negative result can indicate an error, much like UNIX system calls do.

Some signals that are raised to an exception within your code (e.g. or use to share this post with others.