Hi All, Mine is an iOS application (xcode 4.5.2 and iOS 6.1) I make use of a 3rd party library which is written in .C file. There in one of the methods named lookup_txt, the DNS error "kDNSServiceErr_Timeout = -65568" which is an enum is formatted into a string using sprintf. Found that this formatting code is crashing occasionally. Not sure why. Code: char *response = NULL; signed int timeout_error_code = kDNSServiceErr_Timeout; response = (char*)malloc(6); sprintf(response, "%d", timeout_error_code); <----This line crashes occasionally. Below is the extract from apple's crash dump. Code: Thread 7 Crashed: 0 libsystem_kernel.dylib 0x31912350 __pthread_kill + 8 1 libsystem_c.dylib 0x30ebe11e pthread_kill + 54 2 libsystem_c.dylib 0x30efa9f2 __abort + 90 3 libsystem_c.dylib 0x30ec00f6 __chk_fail + 26 4 libsystem_c.dylib 0x30ec019e __sprintf_chk + 54 5 MyApp 0x0028724a lookup_txt (lookup_sd.c:206) Found that sprintf is a macro for __sprintf_chk which appears in the callstack above and also found in _stdio.h. Code: #define sprintf(str, ...) \ __builtin___sprintf_chk (str, 0, __darwin_obsz(str), __VA_ARGS__) Can somebody help me out of the possible reason why this sprintf could be crashing?. Thanks in advance for the help.