以下代码崩溃的可能原因？

Question

I tested the following code on two different compilers, it crashed on first but worked fine on second?

The code is

char *str="testing";
*str='b';
printf("%c",*str);

output : crashed on first compiler

b on second compiler

What may be the possible reason of crash?

Answer 1

The reason for the crash is that writing into a string literal's memory is undefined behavior. Your code *str='b' writes directly into the first char of memory allocated to the string literal. C allows compilers to place the content of literals into the memory area that is protected from writing. Writing anywhere in that region causes a segmentation fault.

Change the declaration to

char str[]="testing";

to avoid the error. If you declare str as a char array (as opposed to a char pointer) the compiler generates code to copy the content of str into writable memory, thus avoiding the error when you write to str .

Answer 2

您正在写入字符串文字，这具有未定义的行为。

Answer 3

通常（和您所看到的一样，取决于系统），字符串文字会被放入只读内存中，然后尝试对其进行更改将导致运行时错误。