问题
Sometimes when I run my code, a core dump file is generated when I terminate the program by Ctrl+\. The file name is of the form core.*. The program is not terminating abruptly, and there is no segmentation fault. I believe it is SIGQUIT and not SIGABRT or SIGSEGV. If I try Ctrl+C, or Ctrl+Z, then it is not generated.
Can anyone tell why it is generated only when Ctrl+\ is pressed? How can I avoid this core dump file from being generated? Is there any use for the core dumped file?
回答1:
A process dumps core when it is terminated by the operating system due to a fault in the program. The most typical reason this occurs is because the program accessed an invalid pointer value. Given that you have a sporadic dump, it's likely that you are using an uninitialized pointer.
Can you post the code that is causing the fault? Other than vague generalizations it's hard to guess what's wrong without actually seeing code.
As for what a core dump actually is, check out this Wikipedia article:
- http://en.wikipedia.org/wiki/Core_dump
回答2:
As said by others before the core dump is the result of a fault in the program.
You can configure if a core dump is to be generated with the ulimit command. Entering
ulimit -c 0
disables core file generation in the active shell.
If the program that generated the core was built with symbol information you can do a post mortem debugging session like this:
gdb <pathto/executable> --core <corefilename>
回答3:
Core dumps are generated when the process receives certain signals, such as SIGSEGV, which the kernels sends it when it accesses memory outside its address space. Typically that happens because of errors in how pointers are used. That means there's a bug in the program.
The core dump is useful for finding the bug. It is an image of the the process's memory at the time of the problem, so a debugger such as gdb can be used to see what the program was doing then. The debugger can even access (sometimes) the values of variables in the program.
You can prevent core dumps from happening using the ulimit command.
回答4:
ctrl + \ sends signal SIGQUIT to the process. According to POSIX.1 standard, the default action for this signal is to generate a core.
SIGILL, SIGABRT, SIGFPE, SIGSEGV are other cases when system will generate a core.
Please refer "man 7 signal" on your system for more details.
回答5:
It's a tool to aid in debugging an application that's behaving badly. It's large because it contains the contents of all the applications physical memory at the time it died as well as the register states and stacks of all its threads.
They get generated when the kernel kills an application for doing something evil, like generating a segmentation violation or a bus error.
回答6:
You can avoid creating a core dump file by writing code that doesn't crash :)
Seriously, core dumps are useful because you can see the state of the program when it crashed, for "post mortem" debugging. You can open them in gdb and inspect the state of your program (especially if it was built with debugging).
Core dumps usually get made if the program has a SIGSEGV (usually caused by invalid pointer dereferencing), SIGABRT (which would happen if you called abort(), or in C++ by the default terminate() handler for exceptions in destructors etc) or some other fault. You can also trigger them explicitly with the debugger or programmatically.
If you've fixed all the bugs and it's perfect, you can delete them. Also, if you've changed your program in any way (and recompiled it) then they will become useless as the debug info now won't match what's in the core dump, so you can delete them then too.
回答7:
The point of Ctrl + \ is to generate a core dump. That's what SIGQUIT does. If you don't want it to be generated, use Ctrl + C (SIGINT) instead. If the program in question is not responding to SIGINT but you need to kill it from the terminal, either you or the developer is doing something wrong.
Programs designed not to be killed from the terminal with Ctrl + C should still respond gracefully to SIGTERM, which can be triggered in another terminal via kill -TERM .... If all else fails, SIGKILL will force an immediate termination.
来源：https://stackoverflow.com/questions/775872/why-are-core-dump-files-generated