It is actually possible in C. You can achieve it in quite a complicated way: 1) Override signal handler 2) Use setjump() and longjmp() to set the place to jump back, and to actually jump back to there. Check out this code I wrote (idea taken from “Expert C Programming: Deep C Secrets” by Peter … Read more
When exactly does segmentation fault happen (=when is SIGSEGV sent)? When you attempt to access memory you don’t have access to, such as accessing an array out of bounds or dereferencing an invalid pointer. The signal SIGSEGV is standardized but different OS might implement it differently. “Segmentation fault” is mainly a term used in *nix … Read more
I could point you to man pages, websites, etc, but ultimately what matters is the C standard itself. As part of the standard runtime library, the usage and behavior is defined in C99-§7.23.2.4 as: #include <string.h> char *strncpy(char * restrict s1, const char * restrict s2, size_t n); Description The strncpy function copies not more … Read more
You are not really dereferencing anything. The argument of sizeof is not evaluated, unless it is a VLA. It is explicitly allowed by the language to put whatever “garbage” you want as the argument of sizeof. The language guarantees that it will not evaluate anything, just perform compile-time analysis of the type of the expression. … Read more
If you use XDebug, there is a maximum function nesting depth which is controlled by an ini setting: $foo = function() use (&$foo) { $foo(); }; $foo(); Produces the following error: Fatal error: Maximum function nesting level of ‘100’ reached, aborting! This IMHO is a far better alternative than a segfault, since it only kills … Read more
You’re blowing the stack with arr and color. Presumably when your call to scanf is commented out the compiler optimises all these variables away, but when it’s present it attempts to allocate memory on the stack. Make the variables global, and read up on stack memory vs heap memory. #include<stdio.h> int arr[10002][10002]; int color[10002]; int … Read more
As per this post, I’ve reinstalled sqlite3 gem and the problem disappeared: gem uninstall sqlite3 gem install sqlite3 My software versions: % ruby -v ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin11.2.0] % rails -v Rails 3.2.1
The rational behind it is simple — how can you check the length of something that does not exist? Also, unlike “managed languages” there is no expectations the run time system will handle invalid data or data structures correctly. (This type of issue is exactly why more “modern” languages are more popular for non-computation or … Read more
From http://www.gnu.org/s/libc/manual/html_node/Heap-Consistency-Checking.html#Heap-Consistency-Checking: Another possibility to check for and guard against bugs in the use of malloc, realloc and free is to set the environment variable MALLOC_CHECK_. When MALLOC_CHECK_ is set, a special (less efficient) implementation is used which is designed to be tolerant against simple errors, such as double calls of free with the same … Read more
Without knowing exactly how this should work I can say that you write outside of the p vector on for (i=0; i < rptr->n; i++) { lptr->keys[lptr->n + 1 + i] = rptr->keys[i]; // When you delete key 84, rptr->n is 4 at one point which takes you outside // p[M] lptr->p[lptr->n + 2 + … Read more