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
You can only longjmp() back up the call stack. The call to longjmp(b_buf, 1) is where things start to go wrong, because the stack frame referenced by b_buf no longer exists after the longjmp(a_buf). From the documentation for longjmp: The longjmp() routines may not be called after the routine which called the setjmp() routines returns. … Read more
raise() can be used to raise a segfault: raise(SIGSEGV);
There are two common kinds of SEGV, which is an error that results from an invalid memory access: A page was accessed which had the wrong permissions. E.g., it was read-only but your code tried to write to it. This will be reported as SEGV_ACCERR. A page was accessed that is not even mapped into … Read more
A char[ROWS][COLS+1] cannot be cast into a char**. The input argument of print_map should be void print_map(char map[][COLS+1]) or void print_map(char (*map)[COLS+1]) The difference being that a char** means to point to something that can be dereferenced like this: (char**)map | v +——–+——–+——+——–+– … | 0x1200 | 0x1238 | NULL | 0x1200 | +—-|—+—-|—+–|—+—-|—+– … … Read more
I got similar problem upgrading to JDK 1.6_18 and it seems solved using the following options: -server -Xms256m -Xmx748m -XX:MaxPermSize=128m -verbose:gc -XX:+PrintGCTimeStamps -Xloggc:/tmp/gc.log -XX:+PrintHeapAtGC -XX:+PrintGCDetails -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=”/tmp” -XX:+UseParallelGC -XX:-UseGCOverheadLimit # Following options just to remote monitoring with jconsole, useful to see JVM behaviour at runtime -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=12345 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djava.rmi.server.hostname=MyHost I still didn’t double check … Read more
“Segmentation fault” message might be generated by a shell. To find out, whether the process is kill by SIGSEGV, check proc.returncode == -signal.SIGSEGV. If you want to see the message, you could run the command in the shell: #!/usr/bin/env python from subprocess import Popen, PIPE proc = Popen(shell_command, shell=True, stdout=PIPE, stderr=PIPE) out, err = proc.communicate() … Read more
Classic Heisenbug. From Wikipedia: Time can also be a factor in heisenbugs. Executing a program under control of a debugger can change the execution timing of the program as compared to normal execution. Time-sensitive bugs such as race conditions may not reproduce when the program is slowed down by single-stepping source lines in the debugger. … Read more
scanf requires the addresses of the variables to be passed to it. Replace your scanf by scanf(“%d %d”,&hour,&min); You should be good to go.