linux 下segmentation fault 的调试

goorage · 发表于 2006-7-4 13:49:00

首先介绍一下segmentation fault，主要就是编程的时候访问了非法的指针，比如空指针，下面是一段权威的描述，结合了操作系统对内存管理和进程的虚拟内存，大家可以看看哦
One of the most common problems when making software is errors like "Segmentation fault", also called SegFault. Here is what a SegFault is. Virtual memory in a computer can be created in 2 ways: pages or segments. Paging means that the memory is divided in pages of equal size, containing words of memory in it. Segmentation means that every process has a segment of memory of needed size, with gaps of empty memory blocks between the segments. The operating system knows the upper limit of every segment, and every segment begins at a virtual address 0. When a program accesses a memory block, it calls a virtual address that the Memory Management Unit (MMU) maps to a real address. If the operating system sees that the requested address doesn't match any valid address in the segment, it will send a signal to the process terminating it. SegFaults are the direct result of a memory error. The program has a bad pointer, a memory leak or any kind of error that makes it access the wrong memory address. To correct these errors you need to check pointers and arrays for errors.

goorage · 发表于 2006-7-4 13:53:00

下面给一个快速发现代码中指针非法使用引起错误的例子。To debug segmentation fault, please following steps: > ulimit –c unlimited # run test image> ./a.out # Segmenation fault happened. You will see the file “core.xxxx” (xxxx is pid) in the directory > gdb a.out core.xxxx > (gdb) bt # Then you will see the segmentation fault point at the File xxxx.cpp : Line xxxx.

goorage · 发表于 2006-7-4 14:05:00

举个例子，我在fedora 下面运行这个代码的, 文件名叫做test.c#include <stdio.h> int main(){ char *p = NULL; *p = 10;}1.编译一下 gcc -ggdb test.c2.输入命令 ulimit -c unlimited3.运行文件 ./a.out发生segmentation falut,同时会生成一个文件core.xxxx(xxxx means pid)4.gdb a.out core.xxxx5.gdb > bt马上就会输出错误代码所在的文件和行数，同时还打印出这句错误的语句。

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[讨论] linux 下segmentation fault 的调试