为什么一个“char *”可以指向“const char *”？ [英] why a "char*" can point to a "const char*"?

问题描述

以下代码可以在VC或gcc上正确编译：

  char * str =I am a const！ ; 
 str [2] ='n'; 
  

然而，显然有一个运行时错误。因为我是一个常数！是一个 const char *，为什么编译器不给出错误或者甚至警告？

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此外，如果我定义 char a [] =I am const！， a 可以修改，为什么这个时候字符串字面值变成 nonconst

解决方案

对于C来说，字符串字面量不是const，它是一个 char [14] ，它分配给一个char *，这是完全正常的。 / p>



但是，C确实说更改字符串文字是未定义的行为。

the following code can be compiled correctly on both VC or gcc:

char *str = "I am a const!";
str[2] = 'n';

however, obviously there is a run-time-error. Since "I am a const!" is a const char*, why the compiler doesn't give an error or even a warning ??

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Besides, if I define char a[] = "I am const!", all the elements in a can be modified, why this time the string literals become nonconst ?

解决方案

As far as C is concerned, that string literal is not const, it's a char[14] which you assign to a char*, which is perfectly fine.

However, C does say that changing a string literal is undefined behavior.

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