const char * 指针问题？

Question

I have some questions related to this simple snippet of code.

#include <string.h>
#include <stdio.h>

int main()
{
   const char *str1;
   str1 = "hello";
   printf("%s \n", str1);
   return 0;
}

I want to ask you:

1. Is it safe to make an assignement to a const char pointer like that? Considering that str1 will never change.
2. Is it possibile that at the time of assignment str1 results NULL?

Thank you all!

Answer 1

Is it safe to make an assignement to a const char pointer like that? Considering that str1 will never change.

Yes. In fact, it's the right thing to do.

The pointer itself is not const ; the type const char* means that the thing it points to is const .

If your pointer were const char* const str1 (a const pointer!) then you wouldn't be able to assign to it later. But you'd also get an error for not initialising it in the first place.

Is it possibile that at the time of assignment str1 results NULL?

No. The literal "hello" is never null. No string literal is ever null.

Answer 2

1. It is safe to do the assignment.
2. After the assignment, str1 will point someplace in the initialized data of the image. Just where is implementation-dependent.

Do not ever attempt to modify the memory at the place pointed to by str1 , for example by aliasing it with a non- const pointer.