Why do I get a segmentation fault when writing to a string initialized with "char *s" but not "char s[]"?

Question

The following code receives seg fault on line 2: char *str = "string"; str[0] = 'z'; // could be also written as *str = 'z' printf("%s\\n", str);While this works perfectly well: char str[] = "string"; str[0] = 'z'; printf("%s\\n", str);Tested with MSVC and GCC.

Answer 1

I suspect in the first case (*str), the linker assigns str to the address of the "hello" string, but the string is stored where the linker places constants. When you try to modify it, the system complains (try removing the str[0]='z' to see if it works without modification).

When you initialize with str[], the linker uses r/w storage to hold "hello" and therefore when you modify the first letter, everything is ok.