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Asked: 2026-05-11T02:04:05+00:00

Why does the following code in C work? const char* str = NULL; str

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Why does the following code in C work?

const char* str = NULL; str = 'test'; str = 'test2';

Since str is a pointer to a constant character, why are we allowed to assign it different string literals? Further, how can we protect str from being modified? It seems like this could be a problem if, for example, we later assigned str to a longer string which ended up writing over another portion of memory.

I should add that in my test, I printed out the memory address of str before and after each of my assignments and it never changed. So, although str is a pointer to a const char, the memory is actually being modified. I wondered if perhaps this is a legacy issue with C?

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  1. You are changing the pointer, which is not const (the thing it’s pointing to is const).

    If you want the pointer itself to be const, the declaration would look like:

    char * const str = 'something';

    or

    char const * const str = 'something';  // a const pointer to const char const char * const str = 'something';  //    same thing

    Const pointers to non-const data are usually a less useful construct than pointer-to-const.

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