Cannot modify C string

Question

Consider the following code.

int main(void) {
    char * test = "abcdefghijklmnopqrstuvwxyz";
    test[5] = 'x';
    printf("%s\n", test);
    return EXIT_SUCCESS;
}

In my opinion, this should print abcdexghij. However, it just terminates without printing anything.

int main(void) {
    char * test = "abcdefghijklmnopqrstuvwxyz";
    printf("%s\n", test);
    return EXIT_SUCCESS;
}

This however, works just fine, so did I misunderstand the concept of manipulating C strings or something? In case it is important, I'm running Mac OS X 10.6 and it is a 32-bit binary I'm compiling.

Answer 1

Char pointers defined with an initialization value go into a read-only segment. To make them modifiable, you either need to create them on the heap (e.g. with new operator or malloc() function) or define them as an array.

Not modifiable:

char * foo = "abc";

Modifiable:

char foo[] = "abc";