Error Usage In C
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Volatile Usage In C
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Extern Usage In C
them; it only takes a minute: Sign up #error directive in C? up vote 21 down vote favorite 4 Can you please give the information about #error directive in C? What is #error directive? what the use of it? #error in c c share|improve this question edited Mar 13 '13 at 23:21 Kornel 62.6k24138199 asked Mar 16 '11 at 5:59 PHP 1,16631739 migrated from programmers.stackexchange.com Mar 16 '11 at 9:38 This question came from our site for professional programmers interested in conceptual questions about software development. 4 This seems more like a question for stackoverflow.com –jmort253 Mar 16 '11 at 6:29 add a comment| 3 Answers 3 active oldest votes up vote 24 down vote accepted It's a preprocessor directive #error c preprocessor that is used (for example) when you expect one of several possible -D symbols to be defined, but none is. #if defined(BUILD_TYPE_NORMAL) # define DEBUG(x) do {;} while (0) /* paranoid-style null code */ #elif defined(BUILD_TYPE_DEBUG) # define DEBUG(x) _debug_trace x /* e.g. DEBUG((_debug_trace args)) */ #else # error "Please specify build type in the Makefile" #endif When the preprocessor hits the #error directive, it will report the string as an error message and halt compilation; what exactly the error message looks like depends on the compiler. share|improve this answer answered Mar 16 '11 at 6:09 geekosaur 34.6k47490 1 That is one paranoid null statement... –Chris Lutz Mar 16 '11 at 9:40 Wouldn't it be more appropriate to say it halts preprocessing? I guess preprocessing can be viewed as a step in compilation, but it can definitely be done as a separate step, and is internally performed as a separate step, so it fails/reports a fatal error earlier on than a compilation error. –RastaJedi Apr 19 at 19:57 add a comment| up vote 12 down vote I may have invalid code but its something like... #if defined USING_SQLITE && defined USING_MYSQL #error You cannot use both sqlite and mysql at the same time #endif #if !(defined USING_SQLITE && defined USING_MYSQL) #error You must use either sqlite or mysql #endif #ifdef USING_SQLITE //... #endif #ifdef USING_MYSQL //... #endif share|improve this answer answe
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#error In C Example
Functions C - Scope Rules C - Arrays C - Pointers C - Strings use of #error directive in c C - Structures C - Unions C - Bit Fields C - Typedef C - Input & Output C -
#error C++
File I/O C - Preprocessors C - Header Files C - Type Casting C - Error Handling C - Recursion C - Variable Arguments C - Memory Management C - Command Line Arguments C http://stackoverflow.com/questions/5323349/error-directive-in-c Programming Resources C - Questions & Answers C - Quick Guide C - Useful Resources C - Discussion 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 https://www.tutorialspoint.com/cprogramming/c_error_handling.htm 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 as a global variable and indicates an error occurred during any function call. You can find various error codes defined in
of a library call. The functions strerror and perror give you the standard error message for a given error code; the variable program_invocation_short_name gives you convenient access http://www.gnu.org/s/libc/manual/html_node/Error-Messages.html to the name of the program that encountered the error. Function: char * https://www.techonthenet.com/c_language/directives/error.php strerror (int errnum) Preliminary: | MT-Unsafe race:strerror | AS-Unsafe heap i18n | AC-Unsafe mem | See POSIX Safety Concepts. The strerror function maps the error code (see Checking for Errors) specified by the errnum argument to a descriptive error message string. The return value is a pointer to this string. The value in c errnum normally comes from the variable errno. You should not modify the string returned by strerror. Also, if you make subsequent calls to strerror, the string might be overwritten. (But it’s guaranteed that no library function ever calls strerror behind your back.) The function strerror is declared in string.h. Function: char * strerror_r (int errnum, char *buf, size_t n) Preliminary: | MT-Safe | AS-Unsafe usage in c i18n | AC-Unsafe | See POSIX Safety Concepts. The strerror_r function works like strerror but instead of returning the error message in a statically allocated buffer shared by all threads in the process, it returns a private copy for the thread. This might be either some permanent global data or a message string in the user supplied buffer starting at buf with the length of n bytes. At most n characters are written (including the NUL byte) so it is up to the user to select a buffer large enough. This function should always be used in multi-threaded programs since there is no way to guarantee the string returned by strerror really belongs to the last call of the current thread. The function strerror_r is a GNU extension and it is declared in string.h. Function: void perror (const char *message) Preliminary: | MT-Safe race:stderr | AS-Unsafe corrupt i18n heap lock | AC-Unsafe corrupt lock mem fd | See POSIX Safety Concepts. This function prints an error message to the stream stderr; see Standard Streams. The orientation of stderr is not changed. If you call perror with a message that is either a
MySQL MariaDB PostgreSQL SQLite MS Office Excel Access Word Web Development HTML CSS Color Picker Languages C Language More ASCII Table Linux UNIX Java Clipart Techie Humor Advertisement C Language Introduction Compiling and Linking File Naming Preprocessor Directives #include #define #undef #if #ifdef #ifndef #elif #else #endif #warning #error Comments Variables Integer Variables Float Variables First Program assert.h Functions ctype.h Functions locale.h Functions math.h Functions setjmp.h Functions signal.h Functions stdarg.h Functions stdio.h Functions stdlib.h Functions string.h Functions time.h Functions NEXT: Comments C Language: #error Directive This C tutorial explains how to use the #error preprocessor directive in the C language. Description In the C Programming Language, the #error directive causes preprocessing to stop at the location where the directive is encountered. Information following the #error directive is output as a message prior to stopping preprocessing. Syntax The syntax for the #error directive in the C language is: #error message message Message to output prior to stopping preprocessing. Example Let's look at how to use #error directives in your C program. The following example shows the output of the #error directive: /* Example using #error directive by TechOnTheNet.com */ #include