Gets Unsafe Error
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How To Use Fopen_s
gets function so dangerous that it should not be used? up vote 95 down vote favorite 53 When I try to compile C code that uses the gets function, I get a warning: warning: the gets function is dangerous and should not be used. I remember this has something to do with stack protection and security, but I'm not sure exactly why. Can someone help define _crt_secure_no_warnings me with removing this warning and explain why there is such a warning? If gets is so "dangerous" then why can't we remove it? c fgets gets share|improve this question edited Oct 14 '15 at 8:13 Lundin 59.7k1186157 asked Nov 7 '09 at 18:55 vinit dhatrak 1,93841623 add a comment| 10 Answers 10 active oldest votes up vote 80 down vote accepted In order to use gets safely, you have to know exactly how many characters you will be reading, so that you can make your buffer large enough. You will only know that if you know exactly what data you will be reading. Instead of using gets, you want to use fgets, which has the signature char* fgets(char *string, int length, FILE * stream); (fgets, if it reads an entire line, will leave the '\n' in the string; you'll have to deal with that.) It remained an official part of the language up to the 1999 ISO C standard, but it was officially removed by the 2011 standard. Most C implementations still support it, but at least gcc issues a warning for any code that uses it. share|improve this answer edited F
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Gets Function In C Not Working
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Fgets Function C
Join them; it only takes a minute: Sign up Getting an error “fopen': This function or variable may be unsafe.” when compling [duplicate] up vote 9 down vote favorite 7 This question already has an answer here: fopen http://stackoverflow.com/questions/1694036/why-is-the-gets-function-so-dangerous-that-it-should-not-be-used deprecated warning 9 answers I'm receiving this error when compiling: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. I'm new to C++ and open CV, therefore please help me to get rid of this error. Thanks void _setDestination(const char* name) { if (name==NULL) { stream = stdout; } else { stream = fopen(name,"w"); if (stream == NULL) { stream = stdout; } } } c++ opencv fopen share|improve this http://stackoverflow.com/questions/21873048/getting-an-error-fopen-this-function-or-variable-may-be-unsafe-when-complin question edited Apr 25 '15 at 22:23 Donald_W 989824 asked Feb 19 '14 at 6:45 SeverusSwan 49113 marked as duplicate by Mat, ApproachingDarknessFish, nvoigt, MSalters, Omar Feb 19 '14 at 17:02 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. add a comment| 2 Answers 2 active oldest votes up vote 27 down vote accepted This is not an error, it is a warning from your Microsoft compiler. Select your project and click "Properties" in the context menu. In the dialog, chose Configuration Properties -> C/C++ -> Preprocessor In the field PreprocessorDefinitions add ;_CRT_SECURE_NO_WARNINGS to turn those warnings off. share|improve this answer answered Feb 19 '14 at 6:51 nvoigt 33.8k83072 1 I would not disable this warning. Instead of this I would use more secure version of fopen, it means fopen_s. See 'Security Features in the CRT' for details. –Bogdan Feb 19 '14 at 6:53 2 @Bogdan Yes, that's nice if you are Microsoft only, but this is an MS extension and not standard C++. If this is a library or part of a project that is not 100% Microsoft only, you should not use the _s extensions but instead rely on writing good standard conforming code instead. –nvoigt Feb 19 '14 at 6:57 3 I don't see why one would write an
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ProgrammingWhy is it unsafe using gets() in C/C++?UpdateCancelPromoted by Metavision.comKeep up with the latest augmented reality (AR) happeningsPokémon GO barely touched on AR's potential. Bookmark these AR sites to stay on top of the industry.Learn More at Metavision.comAnswer Wiki8 Answers Greg Kemnitz, Used a few over the years...Written 68w ago · Upvoted by Toby Thain, C coder since late 1980s on Macintosh, UNIX, and very occasionally Win32. Recent open source person…The function prototype for gets is the following:char * gets(char *str); gets - C++ ReferenceThe problem is there's nothing specifying the size of str, and gets() basically trusted you to give it a big enough str to hold all possible input. Its behavior if the number of input characters is longer than the allocated length of str is undefined (and very bad).This made it easy to implement buffer overrun exploits using this flaw, leading to a whole host of hack attacks, starting with the Morris worm.The replacement function is fgets():char * fgets(char *str, int num, FILE *stream);fgets - C++ Referencefgets() reads until a newline is encountered or until num-1 characters have been read, and puts a '\0' at the end of the characters it reads into str. As long as you've allocated at least num characters for str, fgets() will work safely.5.2k Views · View UpvotesRelated QuestionsMore Answers BelowHow should I start game development in C++ using Android NDK?Why should I use the unsafe context in C# just to enable pointers?Why are pointers used in C/C++?Where is C/C++ used?Why use C instead of C++? Robin Thomas, Using C for more than 10 yearsWritten 59w agoLet's see the syntax of the gets() function.char *gets(char *s);Consider that s is a character array of size 10, i.e. s[10]. It can hold upto 10 characters.If the