gdb调试和编译后运行结果不一致

今天在看代码时，遇到这么一段代码，我但是用g++编译了，运行发现有Segmentation fault。

然后就用gdb跟进去看看，可是gdb却正常执行了。不知道什么原因。

#include <iostream>
using namespace std;

int main(){
	char a[] = "hello";
	a[0] = 'x';
	cout << a << endl;
	char *p = "world";
	p[0] = 'x';
	cout << p << endl;

	return 0;
}　　

以下为运行的情况

stephen@DESKTOP-6NDH281:/mnt/h/dev/c++$ ./a.out
xello
Segmentation fault (core dumped)

以下为gdb跟进去的情况，打印出来了xorld

Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./a.out...done.
(gdb) list
       #include <iostream>
       using namespace std;

       int main(){
               char a[] = "hello";
               a[] = 'x';
               cout << a << endl;
               char *p = "world";
               p[] = 'x';
              cout << p << endl;
(gdb) break
Breakpoint  at 0x40090b: file testpointer.cpp, line .
(gdb) run
Starting program: /mnt/h/dev/c++/a.out
xello

Breakpoint , main () at testpointer.cpp:
              cout << p << endl;
(gdb) s
xorld
              return ;
(gdb) quit

费解啊。后面再看吧。